There has been talk of "rescheduling" cannabis for years, a regulatory move that would significantly ease federal restrictions on the drug. Now, with a recent push from the White House to expedite the rescheduling process, we may see that change come to pass.

Moving cannabis to Schedule III — a less-restrictive classification for drugs — would represent a very important shift in how the federal government treats cannabis research, in that it would officially state that cannabis has medical use. This landmark decision would encourage some of the largest scientific investment in cannabis research to date and help build some of the strongest evidence of the value of cannabis-based therapies.

However, the move to Schedule III should be viewed as a transition rather than an endpoint.

How cannabis is regulated, today

Cannabis has existed in a complicated space in medicine, policy and public perception for decades.

More than 6 million Americans are registered to use cannabis through state medical programs. Clinicians participating in state medical cannabis programs generally "certify" and "recommend" specific cannabis products to certain patients, rather than write traditional prescriptions. Additionally, a handful of cannabis-derived and cannabinoid-based medications have received formal Food and Drug Administration (FDA) approval.

However, since the Controlled Substances Act was enacted in 1970, cannabis has been classified as a Schedule I substance. This category is associated with the highest level of restriction, including substances such as heroin, MDMA, and LSD.

Under federal law, Schedule I drugs are defined as having a high potential for abuse and no currently accepted medical use. Given some cannabis-derived drugs are FDA approved, it may seem contradictory that cannabis remains a Schedule I substance. The key is that federal drug scheduling, FDA drug approval and state cannabis laws are separate legal and regulatory systems.

Federal law classifies cannabis as a Schedule I drug. Separately, the FDA evaluates and approves individual cannabinoid medications for specific medical conditions. Independently, states can authorize cannabis for medical or adult use under their own laws, even though cannabis remains illegal under federal law.

This three-tiered regulatory landscape can be confusing for patients, clinicians and the general public alike.

Rescheduling would be a boon for research

For a few years, federal officials have recommended moving cannabis to Schedule III, which includes drugs with accepted medical uses that are subject to fewer federal restrictions. Ketamine and anabolic steroids, like testosterone, are examples. Compared with Schedule I substances, Schedule III drugs are considered to have a lower potential for abuse and can be prescribed for accepted medical uses under federal law.

Rescheduling cannabis would thus create a regulatory environment that's more favorable to research, which could support the development of future FDA-approved cannabis-based medicines. Researchers are already exploring cannabinoids as potential treatments for conditions including chronic pain, post-traumatic stress disorder, inflammatory bowel disease and sleep disorders, but the available evidence remains limited for many uses.

Evidence is limited, in part, because for decades researchers studying cannabis have faced regulatory hurdles that extend beyond those encountered with many other controlled substances.

Studies using cannabis often require additional federal, institutional and local approvals, compared to research with less-restricted drugs. They have extra requirements around securely storing and handling cannabis. They require detailed record-keeping to document how research materials are received, stored and used, as well as Drug Enforcement Administration registration for the principal investigator conducting Schedule I research.

Additionally, federal restrictions have historically limited researchers' access to cannabis products that reflect those people regularly use, such as commercially available flower, vape products and edible formulations.

This regulatory burden has historically discouraged some universities, healthcare systems and funding organizations from investing in cannabis research. These hurdles have made cannabis studies slower, more costly and smaller in scale than those conducted with more loosely controlled drugs.

Shifting cannabis to Schedule III would help to reduce these barriers, opening opportunities for more universities and healthcare systems to conduct much-needed clinical studies for medical cannabis. It could help researchers conduct the larger, more rigorous clinical trials needed to determine which therapies are truly safe and effective — and which are not.

Such gold-standard studies would better evaluate cannabis' potential benefits and risks, as well its effects in specific medical conditions and appropriate dosing for each. This evidence could, in turn, help reduce the stigma associated with cannabis use.

What rescheduling won't accomplish

Rescheduling cannabis will not automatically make cannabis more accessible to patients or immediately establish where cannabis is beneficial, what doses are most appropriate or which patients are most likely to benefit.

It would not automatically convert existing state cannabis programs into the conventional prescription model used for most Schedule III drugs. And it would not immediately resolve the complexities surrounding state medical cannabis programs, which operate outside the traditional FDA-approved medication pathway.

Unlike most prescription drugs, medical cannabis is an umbrella term that includes hundreds of products that differ in cannabinoid content, formulation, dose and route of administration. Most of those products have not been approved by the FDA, so rescheduling would not automatically place them into the traditional prescription drug system or immediately resolve many of the financial and access barriers patients face when trying to use them.

Without robust follow-up research, rescheduling alone would do little to resolve the uncertainty surrounding many cannabis products.

In short, the greatest benefit of moving cannabis to Schedule III would not be the policy change itself; it would be the opportunity to build a stronger evidence base for cannabis science and medicine. Policymakers may open the door to Schedule III, but researchers, clinicians and regulatory agencies will determine whether this opportunity will actually lead to the appropriate and meaningful advances in cannabis science and medicine.

The value of rescheduling will be measured not by how quickly it changes patients' access to cannabis, but by whether it helps create the scientific foundation needed to guide responsible medical use.

This article is for informational purposes only and is not meant to offer medical advice.

Opinion on Live Science gives you insight on the most important issues in science that affect you and the world around you today, written by experts and leading scientists in their field.

One of the best-known side effects of smoking cannabis is "the munchies," or an intense increase in appetite. One minute someone might feel full, and the next they appear ravenous.

This effect, known scientifically as cannabis-induced hyperphagia, is powerful enough that for regular marijuana users, it can even cause weight gain, a seven-year analysis found.

So what's really going on? Why can cannabis make people want to eat even when they're already full?

The short answer is that tetrahydrocannabinol, or THC, affects the body's endocannabinoid system. This network, found in both the brain and body, is made of naturally produced signaling molecules, called endocannabinoids, and their corresponding receptors. It helps regulate mood, stress, pain, memory, immune responses, and even appetite.

Endocannabinoids act "like a 'dimmer switch,' fine-tuning neural activity to maintain balance, or homeostasis," Ryan McLaughlin, co-director of the Cannabis Research Center and associate director of graduate studies in neuroscience at Washington State University, told Live Science in an email.

The body produces endocannabinoids because the brain needs tight control over how strongly circuits activate, especially when responding to challenges like hunger, McLaughlin explained. Any disruption in this system is "linked to conditions like anxiety, depression and chronic pain, making this system highly relevant to mental and physical health," he noted.

And because THC has phytocannabinoids that target the same endocannabinoid system, understanding it helps scientists sort out cannabis's potential benefits and risks.

THC "hijacks" our appetite circuit

Of the 140 or more types of phytocannabinoids that cannabis plants produce, THC is one of the best known. "THC works by mimicking endocannabinoids and binding primarily to CB1 receptors in the brain," McLaughlin said. Those CB1 receptors show up heavily in brain areas tied to craving and reward, including the hypothalamus, which helps coordinate hunger signals.

When a person is not smoking cannabis, the body's endocannabinoids are usually released briefly and locally, nudging the system toward hunger in a controlled way. But when someone uses cannabis, "THC activates these receptors more broadly and for a longer period of time," McLaughlin said. "In that sense, it 'hijacks' a system that normally fine-tunes neural activity."

That "hijack" is what causes the munchies, as THC turns up the brain's interest in food to more extreme levels for longer than normal.

"When THC activates CB1 receptors in these areas, it enhances the motivational value of food, essentially tricking your brain into thinking it is in an acute fasting state," McLaughlin said.

The munchies isn't about food type

That fasting state helps explain why the munchies don't always look like a dessert binge. In a 2025 study co-led by McLaughlin and others at Washington State University and the University of Calgary, 82 adults ages 21 to 62 were randomly assigned to vape either 20 milligrams of cannabis, 40 milligrams of cannabis, or a cannabis placebo. People who vaped cannabis ate significantly more than those in the placebo group, but it wasn't just junk food.

"Beef jerky was one of the No. 1 things intoxicated people gravitated toward, which I don't understand. Honestly, I would have thought chocolate, chips, Rice Krispies treats — things like that," study co-author Carrie Cuttler, a WSU psychology professor, said in a statement. According to the researchers, water was also among the popular consumption choices.

To further test whether weed affected taste preferences, the researchers also ran tandem experiments in rats at the University of Calgary. The animals could access different foods but had to work for it by pulling a lever.

Sober rats that were already full tended to quit the task. But after ingesting THC, they behaved differently. "You get them stoned again, and even though they're now full and they've eaten, they go right back as if they're starving," study co-author Matthew Hill, a professor of medicine at the University of Calgary, explained in the statement.

Like their human counterparts, the rats were not picky. The researchers expected more interest in carb-rich foods because these foods trigger a release in dopamine, a neurotransmitter that induces a feeling of pleasure, but that's not what they saw. "It just seemed to be any food," Hill said.

Other things can trigger the munchies

While cannabis use is known to trigger the munchies, other factors that affect the endocannabinoid system can create the same effect.

"Sleep deprivation, stress, intense exercise, or just the sight or smell of food can strongly activate appetite circuits in the brain," McLaughlin said.

However, THC takes things a step further. "What is unique about THC is that it enhances both hunger-regulating regions and reward circuits [in the brain], which together can amplify the biological drive to eat as well as the pleasure of eating," McLaughlin added.

Given that THC and other phytocannabinoids are still highly regulated, challenges in understanding the munchies and other effects caused by these substances remain. "One big misconception is that the 'munchies' happens to everyone, every time," McLaughlin noted. In reality, people's responses vary depending on the THC dose, the person's tolerance, the way the drug is ingested and a person's individual bodily makeup.

"Much of what we know comes from self-report rather than tightly controlled laboratory studies measuring actual caloric intake, hormones, and neural activity," McLaughlin said. "But as cannabis laws evolve and research access improves, I think that there will be more attention paid to understanding this phenomenon."

This article is for informational purposes only and is not meant to offer medical or dietary advice.

People who are pregnant or lactating should not use cannabis, newly updated guidelines from the American College of Obstetricians and Gynecologists (ACOG) stress.

The professional group, which in a 2017 report already encouraged OB-GYNs to advise their patients against cannabis use during pregnancy, now recommends that clinicians systematically ask about, or "screen for", cannabis use by their patients before, during and after pregnancy. The updated guidelines, published in September, also say clinicians should educate their patients about the drug's potential risks.

"Just like we talk about tobacco use in pregnancy or alcohol use in pregnancy, cannabis use in pregnancy should be part of the natural conversation," said Dr. Amy Valent, an assistant professor of obstetrics and gynecology at the Oregon Health and Science University (OHSU) School of Medicine who participated in crafting the recommendations.

ACOG recommends universal screening for cannabis through interviews, self-reports and other validated tools, but the professional group advises against biological testing, which uses hair or urine samples to detect cannabis use. Historically, biological testing has disproportionately affected minorities.

"Black patients screen positive for substance use disorders at the same rate as White patients yet are 4-10 times more likely to have a positive drug screen result reported to child protective services," the guidelines emphasized.

Cannabis use on the rise

In recent years, more and more pregnant individuals have turned to cannabis as a "natural" way to alleviate symptoms such as nausea and vomiting. Some also use cannabis to help them cope with the stress and anxiety often associated with pregnancy.

Between 2002 and 2020, self-reported cannabis use has more than tripled among pregnant individuals in the U.S., according to a study published in 2022 that used data from the National Survey on Drug Use and Health. In 2002, 1.5% of pregnant individuals reported using cannabis without alcohol, compared to 5.4% in 2020.

In addition, various studies show that, in the U.S., about 4% to 16% of people use the drug while pregnant.

"With the legalization of it [cannabis] in a lot of states, people are perceiving the risk to be very low," Dr. Alta DeRoo, a board-certified addiction medicine physician, obstetrician-gynecologist and the chief medical officer at the Hazelden Betty Ford Foundation who did help write the guidelines, told Live Science.

However, ACOG points out that there are no uses for cannabis during pregnancy that are backed by medical science and that it can have serious health consequences for newborns.

Growing evidence of serious health outcomes

The updated guidelines are based on a growing body of evidence that links cannabis use around the time of conception and throughout pregnancy with adverse outcomes, including preterm birth, low birth weight and higher rates of neonatal intensive care unit (NICU) admissions.

In addition, evidence suggests cannabis use during pregnancy and lactation could raise the risk of long-term health effects for children, including neurodevelopmental conditions like ADHD.

Studies have shown that THC, the main psychoactive ingredient in cannabis, can cross the placenta and transfer into breast milk. Cannabinoid receptors — "docking stations" that body-made cannabinoids and cannabinoids from plants can land on — are present in the fetus as early as five weeks of gestation, before a person might know they're pregnant.

"Cannabis exposure during pregnancy significantly decreases placental bloodflow, oxygen availability to the baby and causes changes in the placenta that are similar to placental insufficiency or dysfunction," said Dr. Jamie Lo, an associate professor of obstetrics and gynecology at the OHSU School of Medicine who was not involved in writing the guidelines. This placental dysfunction has been documented in both animal and human studies.

Researchers don't know whether there could be a safe amount of cannabis use during pregnancy.

"I think it's very similar to alcohol use, right? We know that there's a specific syndrome that's associated with alcohol use disorder in pregnancy, but we don't actually know if there's a 'safe amount," Valent said. "Therefore, we definitely know that there's harm with alcohol use in pregnancy, but we don't know to what degree people are going to be more or less vulnerable. And so we don't recommend alcohol use in pregnancy."

Cannabis products are not regulated by the Food and Drug Administration in the same way that pharmaceutical drugs are, she added. As such, they can be subject to cross contamination and other quality control issues. In light of that, Valent recommends that pregnant people stay away from all cannabis products, including CBD, the nonpsychoactive ingredient in cannabis.

Educating patients

In its recent clinical consensus, ACOG provided OB-GYNs with more information about the ways they can inform their patients about the risks associated with cannabis use during pregnancy and lactation, as well as better understand the reasons driving their personal use of the drug. ACOG also advised clinicians on how to guide patients toward safer alternatives that fit their needs.

"Parents want the best things for their children, and they're not trying to do something that might harm their children," Lo said. Many pregnant people who use cannabis likely do so "because they just don't know" the risks, she told Live Science. "And for the longest time, we didn't have great data."

Lo added that there's been a "significant surge of newer literature" over the past few years showing the same adverse outcomes associated with the use of cannabis during pregnancy. The new guidelines use stronger language that "gives the healthcare provider tools to actually feel like they're supported by evidence and a [professional] society in their recommendations," she added. "It's not just their personal opinion."

Valent said she hopes the new guidelines will help raise awareness and spark conversations between clinicians and patients.

"Communication is really powerful between a provider and their patient," she said. "Being able to support our patients and make sure that they feel supported along that path to cessation [stopping cannabis use] is really important."

This article is for informational purposes only and is not meant to offer medical advice.

Cannabis smoke can seem gentler than tobacco's, but that impression of marijuana may be deceptive. Deep in the lungs, the drug's chemistry is far from benign, recent research suggests. Some studies have even linked heavy cannabis use to a heightened risk of some cancers, including those of the head and neck.

So is there a clear link between cannabis and cancer, and if so, what causes it?

Each lungful of cannabis smoke is a brew of the high-inducing ingredient tetrahydrocannabinol (THC), fine particulates, and certain carcinogens that are also found in tobacco. But cannabinoids may bring their own twist by quietly rewiring the lungs' immune settings.

"The airway's protective lining weakens, antiviral signals falter, and inflammation flares," said Raphael Cuomo, a scientist working at the intersection of cancer prevention and addiction at the University of California, San Diego. In one study with mice, cannabis smoke dulled both tumor-fighting and infection defenses. In another, THC blunted the effects of immunotherapy, weakening tumor-killing immune cells in the body.

Cannabis also triggers other changes in the immune system, according to studies in humans, cells and lab mice. In the airways, levels of proteins tied to inflammation spike when cannabis is used consistently. A protein called MUC5AC, which lines and protects the respiratory tract, is made in excess in certain cells, hinting at early tissue changes. Cannabis smoke can skew the enzymes that maintain tissue and switch off genes that respond to toxins.

The responses of the lungs' patrol cells — alveolar macrophages — can be stunted. And in the blood, shifts in cellular messengers called cytokines and faint changes in epigenetics become a molecular diary of exposure.

Related: Could cannabis treat cancer someday? Here's what the science says so far

In summary, "cannabis smoke, from its toxic byproducts to THC, can irritate lungs and weaken immunity," Sayantan Bhattacharyya, a cancer systems biologist who will soon be a senior postdoctoral scientist at the University of Limerick in Ireland, told Live Science.

But immune disruption is only one factor that might raise cancer risk. Cannabis smoke may also tug on deeper levers inside cells — the molecular switches that cancers use to grow and spread.

Among these, few are as infamous as the epidermal growth factor receptor, or EGFR. In one of the few studies of its kind, Bhattacharyya examined 83 men with glottic cancer, which affects the voice box, and found that cannabis smokers in the group had markedly higher activation of EGFR and related cancer proteins than either tobacco smokers or nonsmokers.

"EGFR governs [cell] growth, repair, and survival," Bhattacharyya said. "In cannabis smokers, constant activation can fuel unchecked proliferation, speed genetic damage, and hasten the leap toward cancer — triggering earlier onset, faster spread, and treatment resistance." That said, Bhattacharyya's study included only 83 people with one type of cancer, so more work is needed to know if the results are broadly applicable.

Bhattacharyya sees two priorities for future research. One is to develop realistic lab models — such as "organoids," 3D-printed tumors and organ chips — to study how cannabis amplifies EGFR. The other is to probe potentially dangerous additives that might be lurking in unregulated cannabis products, he said.

For all the unsettling biology uncovered in laboratory studies, real-world studies of cannabis smokers tell a mixed story. Some research links heavy cannabis use to higher cancer risk, while others find no clear connection. Still, Cuomo maintains that long-term use of the drug may increase the odds of developing cancer, based on what we know so far.

For people who already have cancer, however, Cuomo has shown that cannabis use isn't linked to an earlier death — a puzzle researchers now call "Cuomo's paradox." In fact, studies have found that, in cancer patients, cannabis can boost appetite and curb chemotherapy-induced nausea, even as its smoke may potentially be planting the chemical and cellular seeds of disease.

The challenge going forward will be to accurately assess both the benefits and harms of cannabis in order to weigh them against one another.

Editor's note: This story was updated on Aug. 21, 2025, to note that Bhattacharyya will hold a position at University of Limerick.

This article is for informational purposes only and is not meant to offer medical advice.

Because eating a cannabis-infused brownie or gummy does not involve inhaling smoke, it may be tempting to think of edibles as a relatively harmless high. However, new research suggests that similar to smoking cannabis, consuming edibles containing the compound tetrahydrocannabinol (THC) may worsen cardiovascular health over time.

The study found that "chronic smokers of marijuana have poorly functioning blood vessels similar to chronic smokers of tobacco," said Matt Springer, a cardiovascular researcher at the University of California, San Francisco (UCSF) whose lab led the new study. "THC edibles also appear to be associated with this problem."

Published May 28 in the journal JAMA Cardiology, these findings may counter commonly held beliefs about the health impacts of weed.

"A lot of people consider marijuana to be totally safe for the cardiovascular system," said Dr. Robert Kloner, director of cardiovascular research at Huntington Medical Research Institutes in Pasadena, California, who was not involved in the new study.

Although scientists have not reached total consensus about the health effects of cannabis, Kloner added, the UCSF study adds to the mounting evidence that the drug contributes to the risk of cardiovascular events, such as heart attacks and strokes. This is especially true for people with coronary artery disease or with other risk factors, such as a high blood pressure or diabetes, that may lead to arterial narrowing.

Cannabis and heart health

To better understand how cannabis affects cardiovascular health, Springer and his colleagues recruited 55 adult participants who fell into three groups: cannabis smokers, THC edible users and cannabis nonusers. To isolate the effects of habitual cannabis smoking or edible use, the study focused on cannabis users who reported using the drug at least three times a week, exclusively through their preferred method.

The study's lead author Dr. Leila Mohammadi, a physician-scientist at UCSF, noted that their study's strict recruitment criteria resulted in a small sample size, which could somewhat limit the findings. However, it also enabled them to rule out other factors that could affect people's blood vessels, such as tobacco use or underlying health conditions.

To gauge each participant's vascular function, the authors temporarily blocked blood flow to the brachial artery — located in the upper arm — with an inflatable forearm cuff. They used ultrasound imaging to measure the artery's diameter before and after releasing this pressure. This measure is reflected as the percentage of diameter change from the baseline measurement.

Springer said this test offers a "window into the future" because if blood vessels cannot dilate properly in response to increased blood flow, that's linked to a higher risk of poor cardiovascular disease outcomes, such as heart attack.

Among the participants who did not consume cannabis, the researchers measured an average vessel dilation of 10.4%. By comparison, cannabis smokers and edible users had an average dilation of 6.0% and 4.6%, respectively. This decrease in dilation is similar to what the researchers observed in an earlier study of chronic tobacco smokers.

The more cannabis people used — as defined by the number of smoking sessions or milligrams of THC consumed via edibles per week — the more dramatic their impairment in dilation was.

To uncover clues as to why cannabis might cause this change in function, the researchers ran a laboratory study to see how the participants' blood samples affected endothelial cells. These cells line blood vessels and release compounds, such as nitric oxide, that spur vascular dilation.

This vessel-widening process can be triggered by a substance called vascular endothelial growth factor (VEGF). But when the researchers exposed endothelial cells in lab dishes to blood samples from cannabis smokers, they found that the blood hampered VEGF-stimulated nitric oxide production in the cells.

However, blood from edible consumers and cannabis nonusers had no effect on the cells' nitric oxide release. That suggests that cannabis smoke and ingested THC affect the cardiovascular system via separate mechanisms. That idea is in line with a prior study from the same team, which found that secondhand cannabis smoke that was stripped of THC still affected the blood vessels of rats that breathed it in.

The new study revealed only an association between cannabis use and vascular function, not definitive proof of how the drug affects blood vessels, Springer acknowledged. Meanwhile, one of his collaborators previously reported that cannabis appears to harden blood vessel walls but does not affect vascular dilation, whereas the current paper reports the opposite findings. So there's more research to be done.

Springer added that because they only recruited habitual users of the drug, people who consume cannabis less frequently may not be affected the same way.

Cannabis is becoming available to a growing number of consumers thanks to efforts to legalize the drug at the state level. However, research into its health effects has not kept up, Kloner said. Because the drug is still illegal at the federal level, cannabis studies remain constrained by strict regulation, making the drug more difficult to study, he noted.

This article is for informational purposes only and is not meant to offer medical advice.

Using cannabis heavily and regularly may raise the risk of head and neck cancers, a new study finds.

The research looked at 20 years' worth of medical records from more than 116,000 U.S. adults with cannabis use disorder (CUD). Estimated to affect 3 in 10 cannabis users, the disorder is defined as problematic cannabis use that leads to significant impairment or distress and involves signs of tolerance — in which someone needs to use more of a drug to get the same high — and dependence, including withdrawal symptoms.

Compared to adults without CUD, these individuals were 3.5 to five times more likely to develop head and neck cancers, according to the new study, published Thursday (Aug. 8) in the journal JAMA Otolaryngology-Head & Neck Surgery. These include cancers of the mouth, throat, voice box, saliva glands and oropharynx, which encompasses the tongue, tonsils and back wall of the throat.

"This is one of the first studies — and the largest that we know of to date — to associate head and neck cancer with cannabis use," senior study author Dr. Niels Kokot, a head and neck surgeon at the University of Southern California Head and Neck Center, said in a statement. "The detection of this risk factor is important because head and neck cancer may be preventable once people know which behaviors increase their risk."

Related: Could cannabis treat cancer someday? Here's what the science says so far

The research pulled data collected between 2004 and 2024 from TriNetX, a trove of patient data from 64 U.S. health centers. In addition to the patients with CUD, the study included data from over 3.9 million people without a diagnosis of the disorder.

The people with CUD were directly compared with people of the same age and sex, and the researchers also accounted for alcohol and tobacco use, which are major drivers of head and neck cancers.

Compared with the control group, people with CUD were more likely to develop every type of head and neck cancer, except hypopharyngeal cancer, which affects the lower throat.

The study did not investigate how patients used cannabis — for instance, whether they smoked or took edibles. Thus, it can't say for sure whether it's the smoke that's driving the cancer, given that cannabis smoke contains some carcinogens that are similar to those in tobacco smoke. Alternatively, it could be that active components in cannabis, such as THC, activate certain enzymes that can fuel cancer.

"The cannabinoids themselves could be carcinogenic, and it could also be that the smoke itself has potential for carcinogenesis," Kokot told NBC News.

The study does have some limitations, however. For example, people's cannabis use was self-reported, and the exact doses they were exposed to are unknown.

While it's too soon to say if the link between heavy cannabis use and head and neck cancers holds up over time, "the implications of the report … are sobering," doctors from the UC San Diego Moores Cancer Center and Xiangya Hospital in China wrote in a commentary about the study.

It's worth noting that the study's data spanned two decades in which cannabis use became more commonplace, they wrote. If cannabis can be confirmed to fuel cancer in some way, we might expect that the rate of head and neck cancers linked to the drug will become more common in line with cannabis use, they concluded.

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Research into the potential medical benefits of cannabis has exploded in recent years, raising one intriguing question: Could cannabis treat cancer?  

It may sound far-fetched that weed — the high-inducing plant that propagandists once warned would cause "reefer madness" — could contain ingredients that shrink tumors. However, experts told Live Science that there is some early evidence that some cannabinoids, the active ingredients found in cannabis, do have anticancer effects.  

"There's no two ways about it: [Cannabis] has anticancer properties," Wai Liu, a senior research fellow at St George's, University of London, told Live Science. "But the problem is, how do you translate that into the clinic — and that's the difficult question to address." 

Here's what we know so far about Mary Jane's cancer-fighting powers.

Related: Runners enjoyed their workouts more after using cannabis, but physically floundered

What are cannabinoids, and can they treat cancer?

The cannabis plant comes in more than 700 varieties, with famous examples including Cannabis sativa and Cannabis indica. Cannabis plants contain substances called cannabinoids, or chemicals that interact with the endocannabinoid system in the brain. Endocannabinoids made by the body help regulate a plethora of biological functions, including eating, learning and pain recognition. 

Plant-made cannabinoids, of which more than 100 have been identified by scientists, plug into this same system and affect its activity. These plant-made molecules include tetrahydrocannabinol (THC), which is largely responsible for the characteristic "high" associated with cannabis, and cannabidiol (CBD), which doesn't produce a high but has been studied for its potential medicinal effects. 

These and other cannabinoids can now be made synthetically in the lab, as well. In fact, two drugs that contain synthetic THC — dronabinol and nabilone — are already approved by the U.S. Food and Drug Administration to treat the nausea and vomiting triggered by chemotherapy. 

However, research studying whether cannabinoids directly shrink tumors is in its very early days. At this point, it's been mainly limited to preclinical studies in human or mouse cells in lab dishes and in animals such as mice. For instance, synthetic and plant-made cannabinoids have been shown to impede the growth of breast cancer in mice; in these experiments, cannabinoids were injected into the area directly around the tumor, as well as colorectal cancer, prostate cancer and skin cancer in cells. 

There are several ways in which cannabinoids have been shown to have anticancer properties, Liu said. For example, in rodent studies, cannabinoids have been shown to inhibit cancer cell growth by flipping specific molecular switches in tumor cells. And in cell studies, cannabinoids have damaged tumors by flooding them with harmful molecules called reactive oxygen species, he said. 

However, it's not all positive — under certain circumstances, THC has been shown to promote tumor growth in animal models. These differences could partly be explained by studies using varying doses and investigating distinct types of cancer, the authors suggested. 

Related: Cannabis poisonings in young kids skyrocketed following legalization of edibles

Have any cannabinoid-based cancer treatments been tested in humans?

For any cannabinoid-based cancer treatments to reach the market, they'd need to be tested in humans. 

"There's a big difference between what you observe in a cell line in a petri dish compared to what will happen if you treat a human who has that cancer," Dr. Mikael Sodergren, head of the Medical Cannabis Research Group at Imperial College London, told Live Science. 

However, so far, there have been only a few small clinical trials, and all have focused on just one type of cancer: glioblastoma, the most aggressive form of brain cancer. Current treatments for glioblastoma have poor survival rates meaning that new approaches are urgently needed. 

In the first trial, conducted in 2006, scientists showed that THC injections directly into the tumors of patients with brain cancer could safely and effectively inhibit their growth. The trial included just nine patients with glioblastoma. So, although these results were encouraging, the sample size of the study was too small to make any firm conclusions about the drug's safety and efficacy. 

In 2021, a separate research group published the results of another early clinical trial, which included 27 people. One group of participants used a mouth spray containing a mixture of CBD and THC in combination with a traditional chemotherapy drug called temozolomide. They received between 3-12 sprays a day (up to 30 milligrams of CBD and 32.4 mg of THC), depending on their maximum tolerated dose. All of the patients had glioblastoma that had returned following standard, first-line therapy. 

This trial included a comparison group that did not use the cannabinoid spray, and by comparison, almost twice as many patients who received the spray were alive after one year. 

It's still unknown how the spray may affect tumor growth, but it's possible that these compounds help push brain tumor cells toward cell death, thereby enhancing the antitumor activity of temozolomide, Dr. Susan Short, a professor of clinical oncology at the University of Leeds in the U.K. who led the research, told Live Science. 

The centres that are running the study are now aiming to recruit around 240 patients into a larger, midstage clinical trial. They hope to be able to share the results of that trial within two years from now, Short said. 

What's still unknown?

Despite this progress, many questions remain about how cannabinoids might fight cancer at the molecular level, as well as which dosage and administration route would work best in humans. 

And, if approved as a cancer treatment, THC would likely have to be combined with another form of cancer therapy, because only low doses could be given to patients to avoid inducing a high, he said. In clinical trials, it would also be unethical to exclude proven treatment methods from patients, so testing the effects of cannabinoid treatment by itself could be tricky. 

In the meantime, the positive signals scientists have seen in cellular models are certainly worth investigating further, Dr. Brooke Worster, an assistant professor of medicine at Thomas Jefferson University in Pennsylvania, told Live Science. Such studies could help clarify how cannabinoids affect cancer cells and which are most promising as treatments.

In the meantime, though, patients should take the results of these studies with a grain of salt, she said. No one should use the early data about cannabinoids to avoid taking treatments that are already known to be effective against cancer, such as immunotherapy and radiation therapy, she said. 

There's a misconception that "natural" treatments are always better for you. But given that there isn't gold-standard proof that cannabinoids can treat cancer, opting for weed over chemo wouldn't be advisable, Worster added. 

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Using cannabis before a run can make those mundane miles more enjoyable, but may make them feel harder to complete, new research suggests.

In a small study of 42 regular runners in Colorado, where the sale of recreational cannabis has been legal since 2014, study participants reported experiencing a mood boost and greater enjoyment during a 30-minute treadmill workout when they had smoked or vaporized cannabis beforehand. However, on average, participants said that they had to put a lot more effort into running after using cannabis, compared to when they ran sober.

"It is pretty clear from our research that cannabis is not a performance enhancing drug," Angela Bryan, co-senior study author and a professor of psychology and neuroscience at the University of Colorado Boulder, said in a statement.

The authors of the study, published Dec. 26 in the journal Sports Medicine, were inspired by earlier research that suggested runners regularly use cannabis while exercising in states where recreational use of the drug is legal, such as Colorado, California and Nevada.

Related: Worms and humans both get 'the munchies,' despite 500 million years of evolutionary separation

While cannabis won't turn a regular runner into an elite athlete, it could encourage people who are less likely to exercise to get motivated to work out, the authors argue.

"We have an epidemic of sedentary lifestyle in this country, and we need new tools to try to get people to move their bodies in ways that are enjoyable," Bryan said in the statement. "If cannabis is one of those tools, we need to explore it, keeping in mind both the harms and the benefits."

Cannabis contains substances called cannabinoids, which include tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is largely responsible for the characteristic "high" associated with weed, in part because it binds to brain receptors involved in the reward system and feelings of pleasure. CBD does not produce a high but has been studied for its potential medicinal properties.

In the new study, the researchers took baseline fitness measurements of the runners during a 15-minute treadmill test and also had them complete a survey about their prior cannabis use, exercise regimes and attitudes towards doing both activities simultaneously. Then, they asked the runners to pick up 1 gram (0.035 ounces) of cannabis from a dispensary; each participant was told to get a strain that mainly contained either CBD or THC.

Participants used their assigned product at home and were then driven to an exercise facility, where they completed a survey before and after running on a treadmill for 30 minutes. The questions probed the participants' moods, their pain levels and how difficult they found the run. Two days later, the participants repeated this process but without the cannabis.

Every runner reported enjoying their workout more when they had used cannabis beforehand. That finding aligns with research that suggests endocannabinoids — body-made substances that chemically resemble compounds like THC and CBD — are involved in producing a "runner's high," the short bursts of euphoria that some people experience during or after exercise. Using cannabis before a run may therefore enhance that runner's high, the authors said.

Related: Genetic risks behind 'cannabis use disorder' found in huge study

However, the people who inhaled the THC-dominant cannabis strains noticed less of an increase in the enjoyment of their run than the CBD group did. In addition, they felt much more effort was needed to complete their workout after inhaling the drug. This could be partly because THC increases heart rate, Bryan said in the statement.

The new study had several limitations. For instance, it didn't include a group who used a placebo drug instead of cannabis, as a point of comparison. In addition, all of the participants had previously used cannabis while exercising, so the fact that they volunteered suggests they likely had a good experience in the past, potentially biasing the results.

Nevertheless, the study authors said this research is a step toward better understanding how cannabis affects exercise.

"Continued research into the impact of cannabis on the subjective experience of exercise — both positive and negative — is critical," they wrote in the paper.

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Scientists have pinpointed gene variants tied to the risk of developing cannabis use disorder, in which people build up tolerance to weed and struggle to cut back despite negative impacts on their life and health.

The disorder has formal diagnostic criteria in the manual for mental health disorders. But "roughly, what it means is cannabis use that becomes problematic and involves tolerance or other biological signs of dependence, like withdrawal," Dr. Joel Gelernter, a professor of genetics and neuroscience at Yale University School of Medicine and researcher with the U.S. Department of Veterans Affairs (UDVA), told Live Science.

To probe potential genetic risks of the disorder, Gelernter and colleagues drew data from the Million Veterans Program, which gathers genetic and medical data from U.S. veterans, as well as other large datasets.

In all, their analysis included the genomes of more than 1 million people, about 64,000 of whom had a cannabis use disorder diagnosis. These included mostly people of European descent, but also those of African, East Asian and mixed ancestries.

Related: How does cannabis get you high?

In each population, the team uncovered key hotspots of genetic variation in the genome — called "loci" — associated with cannabis use disorder. They found 22 loci relevant to Europeans, two each among Africans and East Asians, and one in people with mixed ancestries.

"That's why it's just a crucial need to increase recruitment outside of European ancestry" for genomic research, first study author Daniel Levey, an assistant professor of psychiatry at Yale University School of Medicine and researcher with UDVA, told Live Science. Expanding the dataset will reveal more gene variants that are relevant to each population.

The genetics behind cannabis use disorder

In the new study, published Monday (Nov. 20) in the journal Nature Genetics, hotspots of variation often appeared near genes related to neurons, the nervous system cells that communicate with electrical and chemical messages. This included a gene that codes for a dopamine receptor that's known to be crucial to the brain's reward system and to play a role in addiction.

Other types of neurons that respond to different chemical messengers also cropped up in the data. But "we didn't see cannabinoid receptors pop up to the top," which are the receptors cannabis' ingredients directly plug into, Gelernter noted. It's possible that genes related to cannabinoid receptors would pop up in larger datasets. But for now, "I think most of what we saw is downstream to the direct interaction of ingredients in cannabis with brain receptors," he said.

In addition to identifying loci, the researchers investigated if these genetic traits appeared alongside those related to other disorders and behaviors. They uncovered links between cannabis use disorder and smoking cigarettes, various forms of substance dependence, and symptoms of post-traumatic stress disorder (PTSD).

They compared these genetic patterns tied to cannabis use disorder with patterns previously linked to general cannabis use. The two patterns were quite different — general cannabis use was not linked to PTSD, for example. However, both general cannabis use and the diagnosed disorder were linked to schizophrenia, although the latter was a stronger link. Gelernter said the team plans to further study the link between schizophrenia and cannabis use disorder, since this has been raised in past research.

Finally, the team uncovered a potential genetic link between cannabis use disorder and lung cancer, but this requires more research to fully understand.

"Smoking cannabis does contain combustion products that could be a mechanism for how it's associated with lung cancer," Levey said. "But we need to have more focused studies to disentangle that relationship." That's especially true because cannabis use disorder was also tied to cigarette smoking, a known cause of lung cancer.

 "To what extent might what we observed be attributable to people simultaneously smoking cigarettes?" Gelernter said. At least in their analyses, cannabis use disorder remained linked to lung cancer even after cigarettes were removed from the equation, but further research is still needed to know what that link means.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

One of the two main active ingredients in marijuana has been found in a plant other than cannabis, researchers claim. 

Scientists in Brazil said they've discovered cannabidiol (CBD) in the fruits and flowers of the Jamaican nettletree (Trema micranthum), an evergreen shrub that is native to tropical and subtropical regions of North and South America, AFP reported this summer.  

T. micranthum belongs to the Cannabaceae family of plants, which contains 11 genera and about 170 species. One genus includes the cannabis plants, such as Cannabis sativa, which is used to make marijuana. These plants produce chemical substances called cannabinoids, including the high-inducing substance tetrahydrocannabinol (THC) and CBD, which doesn't give users a high. 

Unlike C. sativa, T. micranthum doesn't contain THC, so it could be an attractive new source of CBD that comes without the legal barriers associated with growing cannabis. 

Related: How does cannabis get you high? 

"As we continue to see more patients prescribed medical cannabis for chronic health problems in the U.K. and internationally it is promising to see novel approaches to the production of cannabidiol and other cannabinoids," Dr. Simon Erridge, the head of research at Sapphire Medical Clinics in the U.K., who was not involved in the new discovery, told Live Science in an email. 

"There must be cautious excitement around this news however, as the researchers have yet to publish data around the quantities of CBD they have been able to extract from Trema micranthum," he said. The techniques used to optimize the extraction of CBD from the cannabis flower, on the other hand, have been refined over many decades, he said.

There has been growing interest in the potential for using medical cannabis to treat a number of conditions, ranging from Parkinson's disease to epilepsy and chronic pain. However, although the practice is now legal in some countries, including in the U.K., and across many states in the U.S., there are still barriers to accessing the drug worldwide. 

"It was wonderful to find a plant (with CBD but) without THC, because you avoid all the mess around psychotropic [psychoactive] substances," Rodrigo Moura Neto, a molecular biologist at the Federal University of Rio de Janeiro who led the recent research, told AFP. 

"That means the potential is enormous," he said. 

Moura Neto and his team have yet to publish their findings, but he told AFP that they hope to expand their research thanks to a public grant. Their upcoming research will involve looking at the best way to extract CBD from T. micranthum and testing whether it could be an effective substitute for medical marijuana. 

In the meantime, "until we have similar data in relation to Trema micranthum, the vast majority of CBD will continue to come from cannabis plants," Erridge said. 

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Just like humans, roundworms may also crave their favorite snacks after getting high on weed, scientists recently discovered. The researchers didn't test the worm's reactions to cannabis itself, but to a compound that activates the same receptors in the brain.  

"The nematodes not only get the munchies, but they get them through the same process as mammals," Shawn Lockery, a professor of biology at University of Oregon, told Live Science. "The effects of cannabinoids in nematodes parallel the effects of marijuana on human appetites."

One of the most well-known effects of smoking or consuming marijuana is an intense increase in appetite, known as "the munchies." Marijuana, or the dried flowers, leaves, stems and seeds of the plant Cannabis sativa, contains a class of chemicals called cannabinoids. These cannabinoids include the main compound behind weed's psychoactive effects, delta-9-tetrahydrocannabinol (THC), and they bind to cannabinoid receptors (CB) in the brain. In this way, these plant-made molecules mimic the action of molecules made by the human body, called endocannabinoids. 

Endocannabinoids are known to regulate appetite and food intake, and in general, past studies have shown a strong link between CB receptor activation and hunger in humans and mammals. This activation induces cravings for food rich in sugars and fats. For example, rats high on THC eagerly gobble up chocolate cake batter and drink copious amounts of sugar water, experiments have shown. However, the effects of cannabinoids on invertebrates, like nematodes, are poorly understood.

Related: How does cannabis get you high? 

In a study published Thursday (April 20) in the journal Current Biology, Lockery and his colleagues treated a species of roundworm called Caenorhabditis elegans to an endocannabinoid and studied their response to food. The roundworm feeds on bacteria in decaying plant matter and produces some of the same endocannabinoids seen in mammals, including anandamide and 2-arachidonoylglycerol (2-AG). 

The scientists exposed worms to high concentrations of anandamide for 20 minutes and then offered them five types of bacteria. These bacteria differed in terms of how quickly they cause nematodes to grow, once eaten. The team found that the worms, now soaked in anandamide, rapidly devoured the growth-promoting bacteria while barely picking at the others. 

Next, the scientists placed the bacteria at different locations in a maze, into which they released the worms. Compared with their untreated peers, the anandamide-doped worms more often scrambled towards the arm that had growth-promoting bacteria and spent more time chowing down on the grub. These observations suggested that the endocannabinoid drove worms to not only prefer growth-promoting food, but also eat it quickly. 

The researchers found that a specific worm cannabinoid receptor — NPR-19 — binds anandamide and seems to mediate this feeding frenzy. The team replaced the worm's gene for NPR-19 with the human gene for the CB1 receptor, the receptor that both anandamide and THC bind in people. They found that anandamide was still able to produce the munchies in the worm by binding to the human receptor.  

"The nematode and human cannabinoid receptors are interchangeable," Lockery said. "This emphasizes the commonality of cannabinoid effects in nematodes and humans, even after 500 million years of evolution." 

This shared experience of having the munchies not only connects nematodes and humans over evolutionary time, but also suggests that the endocannabinoid system likely serves similar functions in many animal species, and that those functions are key to those species' survival. Among these key functions are those involved in controlling food intake and specifically "hedonic feeding," or cravings for tasty, calorie-dense foods.    

At least in nematodes, anandamide may trigger the munchies by making a specific class of smell-detecting, or olfactory neurons more sensitive to favored food odors and less sensitive to non-favored food odors, the team found. These neurons don't carry the NPR-19 receptor, so other neurons with the receptor are likely "sending a message to the olfactory neurons," Lockery said. "The next step is discovering the nature of this signal and the neurons sending it."

Cannabis poisonings in young children have increased in Canadian provinces where they legalized the sale of cannabis edibles, such as gummies, chocolates and baked goods, a new study suggests.

The research, published Jan. 13 in the journal JAMA Health Forum, evaluated rates of pediatric hospitalizations for poisonings in four provinces: Ontario, Alberta, British Columbia and Quebec. 

Dried cannabis flower use and sale were legalized across Canada in October 2018, but individual provinces could then decide whether additional cannabis products could be sold in their jurisdictions. Quebec chose to prohibit the sale of sweets, candies, desserts and chocolates that contain THC (tetrahydrocannabinol), the psychoactive ingredient in cannabis, but Ontario, Alberta and British Columbia legalized such edibles in 2020.

The study authors wanted to see if the provinces that legalized edibles saw significant spikes in hospitalizations for cannabis poisoning among kids; such pediatric poisonings can cause excessive sleepiness, dizziness, trouble walking, trouble breathing and, in very severe cases, seizures. To do so, the team compiled hospitalization records from children ages 9 and younger who were hospitalized between January 2015 and September 2021. 

Related: Why does cannabis smell skunky? 

In the seven-year study period, the four provinces reported 581 total hospitalizations for pediatric cannabis poisoning. Prior to 2018, 120 poisonings occurred; 105 happened in the window between the legalization of flowers and that of edibles; and 356 occurred after the legalization of edibles in Ontario, Alberta and British Columbia. 

Pediatric poisoning hospitalizations due to cannabis represented a greater proportion of child poisoning hospitalizations over time, the researchers found. 

Prior to the legalization of cannabis flowers, cannabis accounted for about 4% to 7% of the pediatric poisonings in each province. After flower legalization, the four provinces saw that proportion increase 2.6-fold to 3.1-fold. And after legalizing edibles, Ontario, Alberta and British Columbia saw that proportion jump an additional 2.2-fold, while Quebec's rates did not change.

"In provinces with legal edibles, approximately one-third of pediatric hospitalizations for poisonings were due to cannabis," the researchers wrote in their report. Specifically, after the legalization of edibles, about 318 out of every 1,000 poisonings were attributable to cannabis.

"The overall increases in unintentional pediatric poisonings occurred despite regulations by Canadian authorities aimed at reducing the incidence and severity of unintentional pediatric poisonings," the authors added. These regulations involved capping the amount of THC in edibles and mandating consumer education campaigns and child-resistant packaging.

Similar trends are occurring in the U.S. as more states legalize edibles. A report published Jan. 3 in the journal Pediatrics found that U.S. poison control centers received nearly 15 times more calls about kids younger than age 6 accidentally ingesting edibles in 2021 than they did in 2017. That's 3,054 calls compared with 207. 

"Our findings suggest that placing restrictions on the sale of visually attractive and palatable commercial cannabis edibles is a key strategy and policy consideration for preventing unintentional pediatric cannabis poisonings for the U.S. and other countries considering legalization of recreational cannabis," the authors of the JAMA study concluded.

The dairy cows wobbled unsteadily on their hooves, their tongues lolled about and the membranes of their eyes reddened. What triggered these odd symptoms? A diet of industrial hemp, researchers say. 

The cannabis-derived product didn't give cows the munchies — in fact, the cows decreased their overall food intake. In turn, they produced less milk, but the milk they did yield contained detectable levels of both delta-9-tetrahydrocannabinol (THC), the primary high-inducing compound in marijuana, and cannabidiol (CBD), which exerts some effects on the body but isn't psychoactive.   

Hemp is not yet an acceptable animal feed additive in the U.S. or Europe, in part due to concerns that the plants' active compounds will find their way into milk, senior author Robert Pieper, temporary co-head of the Safety in the Food Chain department at the German Federal Institute for Risk Assessment, told Live Science in an email. But as the hemp and CBD industries have grown, stakeholders and regulators have theoretically considered using hemp as animal feed, citing its cheapness and nutritional value, Science reported. However, there's not yet enough research to approve the plant for such use.

In a new study, published Monday (Nov. 14) in the journal Nature Food, Pieper and his colleagues found that cannabinoids can slip into the milk of hemp-fed cows, but the risk this could pose to consumers remains unclear. 

Related: Marijuana's history: How one plant spread through the world  

To evaluate the effects of hemp on dairy cows and their milk, researchers fed 10 lactating dairy cows feed containing hemp with different concentrations of cannabinoids, meaning cannabis-derived compounds with drug-like effects. Hemp and marijuana come from the same plant species — Cannabis sativa — but by definition, hemp contains no more than 0.3% THC, while marijuana carries higher concentrations, according to the U.S. Food and Drug Administration (FDA). 

In the first week of the trial, researchers swapped some of the cows' corn-based feed for hemp feed made from whole C. sativa plants, which contained low doses of cannabinoids. Then, for the next six days, they fed the cows a high-cannabinoid hemp feed made from flowers, leaves and seeds of the plants. 

The whole-plant feed had no effect on the cows' health or behavior. But within hours of switching to the flower feed, the bovines' breathing and heart rates fell unusually low. These are "rare symptoms in cows that only occur in the course of serious illnesses or can be pharmacologically induced," the researchers noted. 

The cows drooled, yawned and produced more nasal secretions than usual, and their eyes reddened. They also exhibited "pronounced tongue play." Some cows who ate larger amounts of the flower feed developed an unsteady gait and adopted abnormal postures when they stood still.

Two days after the diet switch, the cows stopped eating as much, and their milk yields declined. "We currently do not have a mechanistic explanation" as to why this occurred, Pieper told Live Science. The flower feed happened to contain more fat than the whole-plant feed, so that could have affected the cows' appetites — but the cannabinoids themselves also may have played a role, the researchers wrote.

The observed changes in the cows resolved within two days of them switching back to their normal diet. THC is the most likely culprit behind the changes, but other cannabinoids and chemicals in the hemp may have contributed to the cows' symptoms.

THC, CBD and other cannabinoids could be detected in the cows' milk at the end of the whole-plant trial and throughout the flower feed trial. Eight days after the latter trial ended, detectable THC and CBD still lingered in the animals' milk. 

The amount of THC detected during the flower feed trial could have some effect on human health, the study authors said. However, at this point, it's not clear if such THC-tainted dairy would get you high. Much more research will be needed before regulators can consider approving hemp as animal feed. 

Cannabidiol (CBD), an active ingredient in cannabis, might help block infection with the virus that causes COVID-19.

But don't go drop a bunch of cash on CBD oils at your local dispensary: The possible effect still needs to be tested in humans. (And definitely don't smoke marijuana to prevent coronavirus infection.) Even if the findings do hold up, they apply to the kind of medical-grade, Food and Drug Administration (FDA)-approved CBD used to treat seizure disorders, not the low-potency stuff available to consumers.

CBD is also no substitute for weapons against COVID-19 that are known to work, such as vaccination and high-quality masks, said study leader Marsha Rosner, a cancer researcher at the University of Chicago who studies immune responses. But the researchers are hopeful that the compound could be an additional tool in the fight against the SARS-CoV-2 virus — and perhaps other viruses. So far, the team has shown that the compound can help mice fight off COVID-19, and they've turned up suggestive evidence that it might be helping humans, too.

"We don't know yet if CBD can prevent COVID, but we think our results provide a strong case for conducting a clinical trial," Rosner told Live Science. "That's really our mantra: We want a clinical trial."

Triggering stress

CBD is derived from the cannabis plant. Unlike tetrahydrocannabinol (THC), the main psychoactive ingredient in marijuana, CBD doesn't cause a high. But it does bind to more than a thousand different receptors in the human body, said Robin Duncan, a biochemist and nutritional scientist at the University of Waterloo in Ontario, who was not involved in the new research. This biological activity has given it a reputation as a health supplement — CBD oils, shakes and other products are available all over the place — but little about CBD's impact on health has been tested or proven.

Rosner and her colleagues stumbled into studying CBD and COVID-19. They were screening compounds for cancer research, trying to trigger an immune response in cells called the host stress response. The host stress response is part of the innate immune response. It's not targeted at any particular pathogen, but when a cell senses a threat, such as an invading virus, this response puts the cell into a defensive state, triggering the release of protective chemicals and helping prevent the cell's machinery from being used to replicate the virus.

CBD seemed surprisingly good at triggering the host stress response, which is important for cells to fight back against viruses, Rosner said, so she and her colleagues decided to study the compound against the novel coronavirus.

They began by treating human lung cells in a lab dish with CBD and then exposing them to SARS-CoV-2, the virus that causes COVID-19. They found that compared with untreated cells, the CBD-dosed cells were much better at staving off infection. The same held true for monkey kidney cells, which are susceptible to the virus. It also held true for the alpha, beta and gamma variants of the coronavirus. (Delta and omicron weren't available when the study was done, Rosner said.)

"We show that CBD can stop replication of SARS-COV2 in cells in a dish and that it acts at least up to 15 hours after infection, so that suggests it might be effective even at early times after viruses enter cells," Rosner said.

Putting CBD to the test

Cells in a dish are one thing; living organisms are another. The researchers next tested the compound in mice, injecting pure CBD into the guts of the animals daily for seven days and then spraying live SARS-CoV-2 into their nasal passages — a surefire route to infection. They then continued the CBD injections for four more days.

Five days after the viral treatment, the researchers measured the viral load in the nasal passages and lungs of the mice. They found that with a low dose of CBD, the viral load was 4.8 times lower in the lungs and 3.7 times lower in the nasal passages compared with untreated mice. With a high dose, the viral load in CBD-treated mice was 4.8 times lower in the nose and a whopping 40 times lower in the lungs than in untreated mice. The infected mice also seemed to be fighting off the pathogen with relative ease: Lab-infected mice typically become ill and lose weight, but the CBD-treated mice showed no symptoms.

CBD is an FDA-approved treatment for some seizure disorders, so some people take regular oral doses of the pure compound, Rosner said. She and her team combed through the medical records of people with seizure disorders, comparing the rates of COVID cases in those taking CBD as a treatment to those with similar demographics and medical histories who weren't using CBD, about 530 in each group. They found that the rate of COVID-positivity in those actively taking CBD was 4.9%, compared with 9% among those not taking it.(However, because it was based on medical records alone, the study couldn't rule out that there might be some unknown differences between the two groups that might independently affect their risk of COVID exposure.)

An immune booster?

With these promising findings in hand, the team then turned to investigating other cannabis compounds, such as cannabidiolic acid (CBDA), cannabidivarin (CBDV), and THC. They found that CBD alone demonstrated antiviral action. In fact, combining CBD with THC, as one might find in recreational marijuana products, reduced CBD's antiviral effect. In other words, smoking or vaping pot won't protect you against COVID-19, Rosner and her colleagues wrote in their new study, which was published Jan. 20 in the journal Science Advances. In fact, smoking or vaping might cause lung damage that can put a person at more risk if they do catch the disease.

The team also investigated why CBD might be having an effect. They found that CBD activates a couple of different protective processes in infected cells. One, known as the "unfolded protein response," works on the cell machinery that gets hijacked by the virus to make more copies of itself; this response helps maintain function in a cell that is under stress. The unfolded protein response is so named because it helps halt the cell's production of proteins and clear misfolded or unfolded proteins that are gumming up the works. CBD also helped trigger the production of interferons, immune system compounds that mount a first-line defense against viral replication within the cell.

The SARS-CoV-2 virus has its own defenses that help it suppress a cell's interferon production; some early research hints that the omicron variant is less severe than previous variants because it doesn't suppress its host's interferon production as much. If CBD is capable of boosting interferon even as the virus tries to suppress it, CBD might help reduce disease severity. 

Similar results have been seen in other labs, including Duncan's. Duncan and her colleagues have studied the effect of CBD on specific genes within SARS-CoV-2 infected cells and found results that complement Rosner's. In that research, which has not yet been peer-reviewed but has been posted on the preprint database bioRxiv, Duncan and her team found that kidney cells infected with SARS-CoV-2 did a poor job of mounting a frontline antiviral defense. But cells treated with CBD and infected showed a marked increase in genes involved in antiviral action.

"Overall, we both saw similar things: us, when we were looking at specific genes; and them, when they were looking at the whole virus," Duncan said.

In another recent study published in the Journal of Natural Products, researchers at Oregon State University reported that cannabigerolic acid (CBGA) and cannabidiolic acid (CBDA) could bind to the coronavirus spike protein and prevent the virus from entering cells. That's a different mechanism of action than shown in Rosner or Duncan's research, as well as different cannabis compounds. That study also focused solely on cells in a petri dish, not in animals or humans. It's not yet clear whether the CBGA or CBDA used in that study could be metabolized effectively to work in a living organism, Rosner said. CBD metabolism is better understood from its use in seizure treatment. 

To apply for clinical trials in humans, scientists have to show preclinical data suggesting that a drug might have an impact and must also show evidence of safety. Rosner and her team have provided that preclinical data, Duncan said, and CBD is already well-known to be safe and nontoxic in most people. The FDA-grade compound is approved for the treatment of seizures in anyone over the age of 1 in the United States.

A study testing whether CBD could prevent infection would require a huge sample size, on the scale of the studies used to prove the efficacy of vaccination, Rosner said. For that reason, it's more likely that the researchers will first launch a clinical trial testing whether CBD could help reduce symptoms or severity if taken right after COVID infection. They hope to move forward with those trials in the near future.

"We need to find a sponsor and we need to find funding, so we've been in conversation with both companies and our government about how to do that most effectively," Rosner said. 

Originally published on Live Science. 

If you've ever taken a whiff of well-preserved, unburned cannabis buds, and thought you smelled something skunky — or, less likely, been on the receiving end of skunk spray and wondered why you reeked of cannabis — you might wonder why the two smell so similar. 

In other words, why does cannabis smell so much like skunk spray? It turns out, the stinky culprits in both substances belong to a family of prenylated volatile sulfur compounds (VSCs), a subset of volatile organic compounds (VOCs), according to a 2021 study published in the journal ACS Omega.

"We suspected that sulfur-containing compounds were the origins of this aroma, just based on chemical intuition as chemists," study lead author Iain Oswald, an analytical chemist at Abstrax Tech, a company that develops aromatic compounds known as terpenes in Tustin, California, told Live Science. After all, "skunks have a bunch of VOCs in their aerosol spray," so perhaps cannabis had similar properties, the team suspected.  

Related: How does cannabis get you high?

The sulfurous origins of the plant's pungency reported in the study were perhaps expected, but the novelty of some of the compounds that the team discovered were not, said Amber Wise. Wise is the scientific director and an analytical chemist at Medicine Creek Analytics, a cannabis-testing lab in Fife, Washington, and was not involved with the study.

"The skunky smell, you know, egg smell, if you want to call it 'fart smell' — those are all sulfur compounds, like that's known, at least to chemists," Wise told Live Science. "The surprising part was that there's sort of unique molecules to cannabis." 

Those compounds include VSC6 and VSC7, which Oswald said have not before been found in any plants.

Cannabis has a complicated scent profile, with more than 200 secondary metabolites — small molecules plants produce to defend themselves against predators, such as insects, or to attract pollinators — contributing to its distinctive aroma. Terpenes are chief among those in terms of concentration; about six of the aromatic compounds can each be individually responsible for up to 50% of the variation in odor between different cannabis strains, or cultivars, the authors wrote in the study. For example, the cannabis strain called OG Kush gets its signature gasoline-like smell from the terpenes β-myrcene and β-caryophyllene, while higher concentrations of terpinolene and D-limonene make the cultivar Jack Herer smell like citrus and wood.

While the role of terpenes in individual cultivar profiles has been well established, Oswald and his colleagues — three of whom, including Oswald, have filed a patent related to their findings — wanted to home in on the compounds that give all cannabis strains their skunky odor.

VSCs have relatively complex structures, which have made them difficult to analyze. Moreover, the concentrations of VSCs — which are also found in hops and the pungent fruit durian — in Cannabis plants are minute compared with terpenes.

"The amount actually in the plant is very low, even though it has a very strong effect on the odor itself," Oswald said. "And that's just because the human nose is very sensitive to these types of compounds, so it doesn't take a lot to go a long way."

To understand the structures of the sulfurous compounds, Oswald and his colleagues employed a custom-built two-dimensional gas spectrometry system, combined with mass spectrometry and sulfur chemiluminescence. These techniques allowed them to identify the structures of each VSC, which numbered seven in total. Of those seven, the scientists noted that five contained a functional prenyl group — a feature of VSCs that are found in garlic.

Related: Why do we love garlic but hate garlic breath?

The scientists then had a trained panel of four members rank the pungency of the diluted VSCs, along with a collection of terpenes and Cannabis flowers, on a scale of zero to 10. The panel noted that VSC3 — which was identified in a 2001 study published in Chemistry — A European Journal as the primary compound in "skunked" beer that has been ruined by exposure to ultraviolet light — most strongly evoked the skunky aroma of cannabis.

"VSC3, by itself, smells like cannabis, essentially at a distance," Oswald said. "The terpenes, by themselves, are very mildly reminiscent."

This was corroborated when the researchers mixed together the top 10 aromatic components of the Bacio Gelato cannabis cultivar but excluded VSC3 — creating a smell that the panel noted was evocative of the strain's floral scent but not its skunky pungency. However, VSC3 doesn't do all of the aromatic heavy lifting on its own.

"There's this synergistic effect," Oswald said. "When we mixed them together, that flavor panel said, 'This is cannabis this; this is definitely it.'"

Oswald also noted that while the 2021 paper mostly highlighted the significant contribution of VSC3 to the cannabis cultivars' funky odor, the compounds VSC4 and VSC5 can also play an important aromatic role.

"VSC3 is by far the most important and correlated the most with the cultivars," Oswald said. "But if we were to ever discover a cannabis cultivator that didn't have VSC3 at all but had VSC4 and VSC5, I promise you, everybody would say that that smells like cannabis."

Originally published on Live Science.

U.S. health officials are warning about the potential dangers of "delta-8 THC," a compound derived from marijuana, after seeing an increase in hospitalizations tied to the substance.

On Tuesday (Sept. 14), both the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) alerted consumers of a recent rise in the availability of products containing delta-8 THC, as well as reports of adverse effects from the products.

Delta-8 tetrahydrocannabinol (THC) is one of more than 100 compounds known as "cannabinoids" found in the cannabis plant. It is similar to delta-9 THC, the psychoactive compound that's primarily responsible for the high people experience from marijuana. Delta-8 THC is estimated to be about 50% to 75% as psychoactive as delta-9 THC, but it's naturally produced in only very low levels in the cannabis plant, according to the CDC. 

For this reason, some manufacturers use chemicals to convert other, non-psychoactive cannabinoids, such as cannabidiol (CBD), into delta-8 THC. This process may create byproducts, or contaminants, that are harmful to people's health, according to the FDA.

Related: 25 odd facts about marijuana

In addition, products containing delta-8 THC are sometimes labeled simply as "hemp," a term that refers to the non-psychoactive parts of the cannabis plant and their derivatives. Such labeling may mislead consumers into thinking that they are taking a product without psychoactive effects, the FDA says. What's more, some products containing delta-8 THC may be labeled with only the delta-9 concentration, rather than total THC content, which would underestimate the dose of THC in the product.

Recently, the American Association of Poison Control Centers (AAPCC) began monitoring adverse events tied to delta-8 THC and found that from Jan. 1 to July 31, 2021, there were 660 reports of delta-8 THC exposure, nearly 20% of which required hospitalization, according to the CDC. Nearly 40% of these cases involved children younger than 18. The FDA notes that manufacturers of delta-8 THC products often package and label the products in ways that appeal to children, including selling the products as gummies, chocolates, cookies or candies.

The FDA separately received 22 reports from December 2020 to July 2021 of people who experienced adverse reactions — including vomiting, hallucinations, trouble standing and loss of consciousness — after taking products with delta-8 THC.

Consumers should be aware that the FDA hasn't evaluated or approved delta-8 THC products for any use, and that companies may market or label the products in ways that put people's health at risk, the FDA says. People should also be aware that products labeled as hemp or CBD could contain delta-8 THC and cause psychoactive effects. Parents should keep products that contain THC or CBD away from children and pets, officials said.

People who experience serious effects from THC or CBD products should call poison control or seek immediate medical care, the CDC says. 

Originally published on Live Science.  

Marijuana users have had many occasions to wonder where their much-beloved — yet much maligned — cannabis plant came from. They need wonder no more: New genetic research reveals that the pot plant has its roots in what is now northwest China, where local strains are most like the original strain of cannabis cultivated more than 12,000 years ago.

The study — the largest ever of the whole genomes of cannabis plants, adding a further 82 genomes to the 28 that had already been sequenced — shows that cannabis was probably first domesticated in early Neolithic times in the region of modern China near its borders with Kazakhstan and Kyrgyzstan, and from there spread as different varieties around the world. 

The researchers identified a "basal type" of cannabis plant from northwest China that was previously unknown, Luca Fumagalli, a geneticist at the University of Lausanne in Switzerland, told Live Science.

Related: 9 weird ways you can test positive for drugs

Because cannabis plants are so widespread now, there's been considerable scientific debate about where it originated, and suggestions have included West Asia, Central Asia and northern China, Fumagalli said.

"People thought the region was more towards Central Asia, mostly because there were a lot of feral [wild] cannabis plants along the roads there," he said. "But this observational data basically contradicted what we got from the genomic analysis."

Instead, the study showed that cannabis plants from Central Asia belonged to the "hemp type," he said, meaning they are tall, unbranching plants with cellulose-rich stems suitable for producing fibers for ropes and textiles. They weren't the so-called basal type, which are suitable for both fiber production and producing psychoactive effects.

Single species

Most biologists now think two different species of cannabis — Cannabis indica and Cannabis ruderalis — are subspecies of the single species within the genus, Cannabis sativa, that was domesticated earlier than about 12,000 years ago.

That age is affirmed by archaeological evidence, which includes traces of ancient cannabis seeds found in pottery from that time in southern China, Taiwan and Japan.

Related: 27 odd facts about marijuana

Fumagalli said the genetic study led the researchers to conclude that all cannabis plants alive today are descended from plants that were domesticated in the original region, and that the wild progenitors of Cannabis sativa are probably now extinct.

The different types of cannabis would have started to diverge from the basal type sometime after it was domesticated, and the study showed the hemp type became prominent about 4,000 years ago, presumably as people started to select plants for fiber production, he said.

Hemp-type strains of cannabis now grow in the wild throughout Europe, Central Asia and some parts of northern China. The strains of cannabis now grown commercially for drugs are exclusively from the drug-type, which were selected for the higher levels of psychoactive chemicals they produced; and feral drug-type strains now grow in the wild throughout South and Southeast Asia, where cannabis seems to have been cultivated over the past few thousand years, mainly for marijuana's psychoactive effects, he said.

High times

Most prominently, the four types of cannabis differ in the assemblies of genes that control their production of two particular acidic cannabinoids — CBDA, which produces the chemical CBD and is prominent in the hemp-type variety, and THCA, which produces the more psychoactive chemical THC. 

Within the plant, both CBDA and THCA are produced by and compete for the same raw material, cannabigerolic acid or CBGA. Scientists think that both groups of genes probably play a major role in the plant's defenses. Even so, the genes have produced very different effects on the cultivation of each type of plant, with the hemp-type favoring the production of the CBDA genetic assembly and the drug-type favoring the THCA genetic assembly, the researchers wrote.

They noted that cannabis has long been seen as an important source of fiber for textiles as well as a source of medicinal and recreational drugs but that the history of its domestication has been difficult to determine — because of both legal restrictions and clandestine breeding for drugs. 

That is now starting to change, however. "Our study provides new insight into [the] global spread of a plant with divergent structural and biochemical products, at a time in which there is a resurgence of interest in its use, reflecting changing social attitudes and corresponding challenges to its legal status in many countries," the researchers wrote.

The new genetic research is intended to serve as a resource for medical and agricultural research into cannabis . "East Asia has been shown to be an important ancient hotspot of domestication for several crop species, including rice, broomcorn and foxtail millet, soybean, foxnut, apricot and peach. … Our results thus add another line of evidence for the importance of this domestication hotspot."

The study was published Friday (July 16) in the journal Science Advances.

Originally published on Live Science.

A woman's chronic itch defied all types of treatment, from steroids to opioids to light therapy, but it finally dissipated after her doctors told her to try cannabis.

The woman had dealt with chronic itch symptoms — medically known as chronic pruritus — for a decade, according to a report published April 9 in the Journal of the American Medical Association (JAMA) Dermatology.

Chronic pruritus specifically refers to itching that persists for more than six weeks, and the symptom can be associated with a variety of diseases, including eczema, hyperthyroidism and certain nerve disorders, according to a 2013 report in the New England Journal of Medicine (NEJM). In the woman's case, her pruritus derived from a disease of the bile ducts of the liver called primary sclerosing cholangitis. 

Related: 27 oddest medical cases 

There are several theories as to how this disease leads to itchiness but generally, the condition disrupts the normal production of bile, which can lead to a buildup of irritating chemicals under the skin, according to "Itch: Mechanisms and Treatment" (CRC Press/Taylor & Francis, 2014). 

Due to her bile duct condition, the woman also developed lichen amyloidosis, in which raised, dark, itchy bumps appear on the skin and sometimes meld together into thick plaques. The woman had these plaques on her trunk and limbs, accompanied by "extreme" itchiness. 

The woman's primary sclerosing cholangitis was kept under control with medicine and remained stable through time, but her itchiness did not improve. Doctors had previously prescribed a laundry list of treatments to combat this pervasive itching, including topical and oral corticosteroids; an opioid nasal spray; naltrexone, which works against the effects of opioids; and phototherapy, which involves exposing the affected skin to ultraviolet light. 

When all these treatments proved unsuccessful, her doctors turned to medical cannabis. Previous studies have hinted that topical and synthetic cannabinoid treatments can provide at least some relief from itchiness, they noted in the JAMA report. In addition, laboratory studies in animals and cells have hinted at possible explanations as to how the drugs dial down itchy sensations, according to a 2020 review in Journal of the American Academy of Dermatology 

They recommended she use cannabis two nights a week, either by smoking medical marijuana with 18% tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis, or by taking cannabis in tincture form by placing a liquid extract under her tongue.

"Within 10 minutes after the initial administration, her Worst Itch Numeric Rating Scale (WI-NRS) score improved from 10 of 10 to 4 of 10," her doctors wrote in the JAMA report. This scale ranges from 0 ("no itch") to 10 ("worst imaginable itch"). 

The doctors followed up with the woman after five months of treatment and then again after a full year, and they found that she consistently rated her average daily itchiness as 4 out of 10, a drastic improvement from her previous 10 out of 10. At the 16-month and 20-month follow-ups, her itchiness rating plummeted even lower, falling to 0 out of 10.

"Aside from mild sedation, she reported no adverse effects," her doctors wrote. In addition, "she reported an improvement in quality of life," based on a scoring system called the Dermatology Life Quality Index. She was also able to stop taking her other prescribed medications.

The exact mechanism by which cannabis reduced the woman's itching is unknown, but her doctors presented several theories. 

For instance, THC binds to various receptors in the endocannabinoid system, increasing the activity of some while decreasing that of others. The activation of CB1 receptors in the spinal cord and brain, and of both CB1 and CB2 receptors in nerves elsewhere in the body, has been associated with increased pain thresholds, lower nerve cell activation and decreased inflammation, they wrote. In addition, a receptor called TRPV1 helps trigger our sensation of itch, and cannabinoids lock this receptor into a "closed" position, effectively blocking its itch signals.

While this particular patient benefited from the use of cannabis with minimal side effects, the risks and benefits of the treatment still need to be assessed on a larger scale, "especially in its various routes of administration," the doctors wrote. Cannabinoid use has been linked to cognitive impairment, loss of motor coordination, and when smoked, chronic bronchitis symptoms, they wrote in the study.

So while the results of the woman's case are "promising … randomized clinical trials are needed to confirm the results," the doctors wrote. Other researchers have called for such trials in the past, in order to evaluate the benefits of cannabis for chronic itch and to standardize dosing and the course of treatment, according to the Journal of the American Academy of Dermatology report.

Originally published on Live Science. 

People with chronic migraines who use cannabis products are much more likely to suffer from "rebound headaches" than those who don't use the drugs, a preliminary study suggests.

However, though a link has been uncovered, it's still unclear whether cannabis directly triggers the rebound headaches, the study authors told Live Science. The study also didn't specify what types of cannabis products the patients used, so it's unknown whether certain products show a greater correlation to rebound headaches than others.

A rebound headache, also known as a medication-overuse headache (MOH), happens when a person who already has a headache disorder, such as chronic migraine, either develops a new kind of headache or their existing headaches significantly worsen over time because they are taking headache medication too frequently, according to the International Classification of Headache Disorders (ICHD 3).

A formal diagnosis of rebound headaches means that a person has regularly overused one or more drugs to treat their headaches for more than three months. That usually means taking pain-relieving or antimigraine medications more than two or three days a week, according to Harvard Health. In addition, a diagnosed person will have experienced headaches on 15 or more days each month. The rebound headaches usually resolve if patients stop overusing the medications.

Related: Ouch: 10 odd causes of headaches 

These headaches affect about 1% to 3% of people in the general population and nearly one-third of the patients who seek treatment for headaches at specialized clinics, such as the Stanford Headache Center, study author Dr. Niushen Zhang, a clinical assistant professor and director of the Headache Fellowship Program at Stanford University School of Medicine, told Live Science in an email.

Now, in their new study, Zhang and her colleagues found that people with chronic migraines appear six times more likely to experience rebound headaches if they use cannabis, as compared with migraine patients who don't use the drug. The scientists will present the unpublished research at the American Academy of Neurology's 73rd Annual Meeting, to be held virtually in April.

"This study shows that there is some kind of association between cannabis use and medication-overuse headache in people with chronic migraine," Zhang said.

However, the research is still in its early days, and "it is unclear at this time whether patients are using cannabis to treat medication-overuse headache or if cannabis is contributing to the development [of] medication-overuse headache, or both," Zhang said. Future studies will be needed to determine whether cannabis contributes to the emergence of rebound headaches, and if so, what that means for those with chronic migraines, she said. 

For now, "it is too early to provide any clinical recommendations based on the current findings," Zhang added. 

Zhang and her colleagues launched their study after noticing that a number of their patients with both chronic migraines and MOH also used cannabis products, she said. As there is very little research on cannabis use and these headache disorders, the team decided to explore the association further. 

"Our study is the first of its kind to assess the risk of medication-overuse headache in chronic migraine patients who use cannabis," Zhang said.

The team pulled data from the Stanford Research Repository Cohort Discovery Tool, collecting information on chronic migraine patients treated between 2015 and 2019. They included 368 adults who had experienced chronic migraine for at least a year; 150 reported using cannabis products, and 218 did not use any. 

The team then assessed which patients had been diagnosed with MOH, taking other variables into account, such as how often they got migraines, how long they'd been using cannabis, when they got diagnosed with MOH and what other medications they took for headaches. 

They found that 212 patients had MOH, and that patients who reported cannabis use were far more likely to be diagnosed with the disorder. There was also a significant link between cannabis use, opioid use and rebound headaches, they found. "Some of the patients in the study who were using cannabis were also taking, or had a history of taking, opioids," Zhang said. 

Again, future studies will need to investigate if and how these drugs raise the risk of rebound headaches, as well as what happens when people take them simultaneously. 

The cannabinoids in cannabis products bind to receptors in the body that regulate the perception of pain, and there is evidence that cannabis products can help alleviate certain types of chronic pain, Live Science previously reported. That said, since this new study reveals a potential link between the drugs and rebound headaches, more research will be needed to see whether cannabis sets migraine patients up for worse headaches, Zhang said.

Again, for now, it's too early to say for sure.

Originally published on Live Science. 

Women who use marijuana while they are figuring out how to get pregnant may be less likely to get pregnant compared with those who don't get high, a new study suggests.

The study researchers found that, among women trying to get pregnant, those who reported using marijuana or who had a positive urine test for the drug were 40% less likely to get pregnant during each monthly cycle, compared with those who didn't use marijuana.

In addition, marijuana users had differences in levels of certain reproductive hormones, which could potentially affect their pregnancy chances.

"These results highlight potentially harmful associations between cannabis use and reproductive health outcomes," the researchers, from the U.S. National Institutes of Health (NIH), wrote in their study, published Monday (Jan. 11) in the journal Human Reproduction.

Related: How to get pregnant: 10 tips for women

However, the authors note that only a relatively small number of women in the study used marijuana, which limits the robustness of the study findings. And they did not assess marijuana use in women's partners, which could also affect conception chances. The study does not prove that using marijuana directly causes fertility problems — only that there's a link between use of the drug and lower odds of conception.  

In addition, the study involved a sample of women who had experienced a previous miscarriage, and so it is unclear if the findings would apply to the general population.

Still, until more research is available, the authors say that women should be cautious about marijuana use while trying to conceive, according to a statement from the NIH.

Marijuana and fertility 

The American College of Obstetricians and Gynecologists already recommends that women who are pregnant or trying to become pregnant  discontinue marijuana use, given concerns about the effect of the drug on the fetus' brain development. 

However, few studies have examined the effects of marijuana use on fertility. Of the small number of studies that have been conducted, all relied entirely on self-reports, which may underestimate marijuana use given the stigma of substance use.

The study researchers analyzed information from more than 1,200 women ages 18 to 40 who were trying to conceive and had experienced one or two prior miscarriages. These women, who were from four states (Pennsylvania, New York, Utah and Colorado) were originally part of a separate study looking at the effect of low-dose aspirin on pregnancy outcomes from 2006 to 2012.

The women were followed for six months while they were trying to conceive. At the start of the study, women reported if they had used marijuana, pot or hashish in the past 12 months. They also provided at least two urine samples — one at the start of the study, and another six months later if they hadn't conceived, or at the time of pregnancy if they did conceive. 

Overall, 62 women (5% of participants) either reported marijuana use in the past 12 months or had a positive urine test. (A total of 44 women self-reported marijuana use, and 33 had a positive urine test, meaning that 18 women who didn't admit to using marijuana had indeed used the drug.)

By the end of the six-month study, 42% of marijuana users had become pregnant, compared with 66% of non-users, the researchers found. And marijuana users were 41% less likely to conceive each cycle, compared with non-users. The findings held even after the researchers took into account factors that could affect fertility, such as age and body mass index (BMI) as well as alcohol use.

Studies in animals have found that marijuana may affect the lining of the uterus and make it less likely for an embryo to successfully implant, the authors said. They call for further research exploring the effects of marijuana on fertility, particularly given the increasing legalization of the drug.

Originally published on Live Science.  

Young adults aren’t drinking as much as they used to. In fact, more than a quarter don’t drink alcohol at all, recent surveys show.

It’s good news for health. But there is also a downside in the data: While alcohol use is falling among 18-to-22-year-olds, marijuana use is inching upward. The number of young adults using both alcohol and marijuana is also rising, heightening concerns about a future surge in substance abuse problems, new research shows.

I am a professor of psychology at Texas State University who has been studying young adult and adolescent substance use for over 15 years. A key interest of mine is how substance use changes over adolescence and young adulthood. It is a period of profound change: A 13-year-old is very different from a 25-year-old in nearly every way.

With colleagues at the University of Michigan, the University of Central Florida and Iowa State University, I have been investigating trends in alcohol and marijuana use in young adults to better understand how use changes with age. The latest numbers offer both hope and concern.

Gen Z is breaking stereotypes

There are reasons for the stereotype of hard-drinking, substance-using young adults, as photos and videos from bars and college parties will attest. But surveys and our analysis suggest that binge drinking isn’t as common as people may believe it is.

Using data from the annual National Survey on Drug Use and Health, we found that in 2018 nearly 30% of college-age adults, ages 18-22, had not had a single alcoholic drink during the previous year, compared with fewer than a quarter in 2002. Over 60% had not used marijuana at all.

Among 18-to-25-year-olds, the number who reported binge drinking in the previous year fell from 39% in 2015 to 34% in 2019. That may be influenced at least in part by beliefs that are forming in high school. Another survey shows that nearly three-quarters of high school seniors think their friends would disapprove of weekend binge drinking, up from just over half in the early 1980s.

Adolescents – typically 12 to 17 years of age – were more likely to avoid both alcohol and marijuana than they were two decades ago, part of a larger trend in declining substance use and risky behavior among adolescents seen in a variety of national surveys and data sources. In 2019, nearly 80% of adolescents had not used alcohol at all in the previous year, compared with 65% in 2002, and 87% had not used marijuana.

Using both marijuana and alcohol

The bad news is that the number of college-age young adults saying they used marijuana at least once in the previous year has increased, from 33% to 37%.

The vast majority who said they used marijuana also used alcohol. We found that the increase in young adults using both was a result of young adults who used alcohol taking up marijuana, too.

This increase in using both alcohol and marijuana is an important warning sign, because young adults in that group also had much higher rates of other illicit drug use, like cocaine, and prescription drug misuse, involving medications like opioids or benzodiazepines.

That may signal that a greater number will need substance use treatment in the coming years.

Why the changes?

One theory for the shifting trends in alcohol and marijuana use is that adolescent substance use is now starting at later ages.

The data support this: The numbers of adolescents starting alcohol use has declined somewhat, while more college-age adults are first-time alcohol and marijuana users. Why that shift is occurring is less clear, but one theory is that adolescents have been engaging in more virtual contact than face-to-face contact in recent years and they rarely use substances when they’re alone.

Changing regulations likely also play a role. Marijuana is now legal for medical or recreational use in an increasing number of states.

Attitudes toward alcohol and marijuana have also changed over the years, particularly for marijuana.

The Monitoring the Future study, which has tracked substance use in adolescents and young adults since 1975, indicates both a sharp decline in disapproval of marijuana among middle and high school students and a decline in how harmful they perceive marijuana to be. In fact, more young people in that age group now see more harm from regular alcohol use than disapprove of marijuana.

[Deep knowledge, daily. Sign up for The Conversation’s newsletter.]

How the pandemic will change young people’s habits with alcohol and marijuana isn’t yet clear. One survey conducted this spring when many restaurants and bars were closed found that adults over 30 were drinking alcohol 14% more often. However, when researchers in Australia homed in on younger adults in Gen Z, they found a different story: Older age groups may be drinking more, but with bars and restaurants closed, 44% of the college-age crowd reported drinking less.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Live Science.

Have you ever looked at your hands? I mean really looked at your hands? 

You might think you have, but as the above classic Doonesbury cartoon implies, people who are high on cannabis may perceive mundane objects to be far more fascinating than usual.

How is it that a plant that first emerged on what's now the Tibetan Plateau can change humans' perception of reality? The secret lies in a class of compounds called cannabinoids. While cannabis plants are known to produce at least 140 types of cannabinoids, there's one that's largely responsible for many of the effects of feeling high. It's called tetrahydrocannabinol, or THC. 

Related: Why does alcohol make you sleepy, then alert?

When a person smokes or inhales cannabis, THC "goes into your lungs and gets absorbed … into the blood," according to Daniele Piomelli, a professor of anatomy & neurobiology, biological chemistry, and pharmacology at the University of California, Irvine School of Medicine. Edibles take slightly longer trip through the liver, where enzymes transform THC into a different compound that takes a bit longer to have an effect on people's perception of reality. 

THC that's inhaled "reaches pretty high levels fairly quickly," Piomelli told Live Science. Within 20 minutes, the circulatory system is carrying molecules of THC to every tissue in the body, including the brain, where it can alter neural chemistry.

"From the lungs, it's a pretty straight shot to the brain," according to Kelly Drew, a professor of chemistry and biochemistry at the University of Alaska Fairbanks. 

The THC molecules that pass the blood-brain barrier will find that they fit snugly into receptors that ordinarily receive compounds called endocannabinoids, which the body produces itself. These receptors are part of the endocannabinoid system, which is involved in several functions, including stress, food intake, metabolism and pain, according to Piomelli, who also directs the Center for the Study of Cannabis at UC Irvine. 

"The endocannabinoid system is the most pervasive, diffused and important modulatory system in the brain because it controls the release of pretty much every neurotransmitter," Piomelli said. Neurotransmitters are molecules that brain cells, or neurons, use to communicate with each other. One neuron sends a message to the next by releasing neurotransmitters, such as dopamine or serotonin, into an infinitesimal gap that separates one neuron from the next. The gap is called the synapse.

The neuron on the receiving end of the synapse is called the postsynaptic neuron, and it "decides whether to fire based on the input it receives," Drew told Live Science. These neural signals cascade through intricate circuits of neural connections that function on a tremendous scale; there are about 85 billion neurons in the brain and as many as 100 trillion connections among them. 

The presynaptic neuron sends neurotransmitters across the synapse to the postsynaptic neuron, Piomelli said. But the presynaptic neuron can also receive information. When a postsynaptic neuron has fired, it can send a message across the synapse that says, "the neuron I come from has been activated," stop sending neurotransmitters, Piomelli said. It sends this "stop" message in the form of endocannabinoids that bind to a receptor called cannabinoid 1 (CB1).

Related: What's worse for your brain — alcohol or marijuana?

"Like a sledgehammer"

When THC enters the brain, the molecules diffuse into the synapses where they "activate CB1 receptors," Drew said. THC doesn't cause the most extreme possible response like some synthetic cannabinoids such as K2 or spice, but it does "turn up the volume" and increase the likelihood that the presynaptic neuron it affects will temporarily stop sending neurotransmitters, she said.

"The high is a very simple phenomenon, Piomelli said. "THC comes in like a sledgehammer," flooding the endocannabinoid system with signals the postsynaptic neurons didn't send. When presynaptic neurons across the brain get the memo to stop sending neurotransmitters, this alters the normal flow of information among neurons and results in a high.

Scientists have yet to decipher exactly what happens during this euphoria, however. 

That's because, in part, U.S. legal restrictions make it difficult to study cannabis. But from what researchers have gathered so far, THC appears to temporarily "unplug"  the default mode network. This is the brain network that allows us to daydream and think about the past and future. When our brains are focused on a specific task, we quiet this network to let our executive function take control. 

There's evidence that THC has a significant effect on the network, but researchers aren't quite sure how it happens. There are cannabinoid receptors all over the brain, including in "areas that constitute the key nodes of the [default mode network]," Piomelli said. It could be "that THC deactivates the [default mode network] by combining with those receptors," but it's also possible that THC quiets the network through an "indirect effect that involves cannabinoid receptors in other brain regions."

Scientists are still working to find the mechanisms that result in a person feeling high, but there's some reason to think this effect on the default mode network is a significant piece of the puzzle. 

Unplugging the default mode network "takes us into a mental place where the function of the things we experience is less important than the things themselves: our hands are no longer just something we use for touching or grabbing, but something with inner existence and intrinsic value," Piomelli said. Psychedelics, such as LSD or dried psilocybin-containing mushrooms, do the same thing.

However, people can experience highs differently. "The feeling of becoming fascinated by and 'connected' with ordinary things, things we see and use every day, is not universal but does happen, especially when high doses of THC-containing cannabis are used," Piomelli said.

Related: 25 odd facts about marijuana

THC doesn't just affect the default mode network. It may also, in the short-term, flood the brain with dopamine, the brain's reward signal, according to a 2017 study in the journal Nature. (Long-term, it may blunt dopamine's effects, the study found.) That, in part, may explain some of the euphoria associated with a high, and places cannabis in the company of other drugs that people use to feel pleasure.

"Every drug that has rewarding properties affects that system," Drew said.

Aftereffects 

The effects of a high from cannabis that's smoked or inhaled typically last for a few hours, though it can take edibles almost that long to start affecting users. And while cannabis isn't the dangerous substance it was made out to be in the 20th century, using it comes with some risk. For one, while cannabis is legal for recreational and medical use in some states, it's still illegal in many parts of the country. 

It's also important to bear in mind that cannabis is a potent pharmacological substance. Cannabis can cross the placenta, so pregnant people should avoid it. And "heavy use in the teenage years can be problematic," Piomelli said. For instance, cannabis — and especially synthetic cannabinoids like spice — can exacerbate psychosis. "People who are at risk for that should not smoke it," Drew said.  

Finally, cannabis does affect the ability to drive, particularly in occasional users. Drew cautioned that people should not drive for three hours after smoking.

Eventually, the THC will leave the brain; the profusion of blood that brought THC into the brain will carry it to the liver, where it will be destroyed and expelled in urine. 

And you're not gonna believe this, but your hands — they were the same the whole time. 

Originally published on Live Science.

A zoo in Poland plans to test cannabidiol — also known as CBD, a chemical found in cannabis — on its elephants, for stress relief.

According to the BCC, the Warsaw Zoo's decision follows the March death of Erna, the elder elephant in the herd. Elephants are matriarchal, meaning older females lead the herd, so it's no surprise that the three younger elephants have shown signs of stress since her death. Zookeepers hope the CBD will help calm the tense animals; elephants get stressed out easily and are relatively easy for the zoo to keep an eye on, so they're good candidates for testing the substance, which is touted for its calming effect on humans, the zoo told BBC.

As Live Science previously reported, CBD is one of a range of chemicals found only in cannabis plants. But unlike tetrahydrocannabinol (THC), marijuana's main psychoactive ingredient, CBD doesn't cause humans to get high

Related: 25 odd facts about marijuana 

CBD is an increasingly popular substance in the natural wellness industry, and there's anecdotal evidence to suggest it's effective for treating anxiety and other ailments. Proponents of the compound have hailed CBD's healing effects for a wide range of physical and mental illnesses, such as depression and cancer. However, due to U.S. laws regulating the production, use and testing of marijuana products, research on the effects of CBD is limited, although one clinical trial published in the New England Journal of Medicine in 2017 did find that CBD reduced seizures in people with Dravet syndrome, a rare form of epilepsy. As Live Science reported, some early studies have suggested that CBD may work to combat anxiety, and psychosis, while others indicated that it's no more effective than a placebo.

And, of course, all that research describes the effect of CBD on humans. No research yet exists to indicate how the cannabinoid will impact elephants, though CBD companies do make products targeting dogs and cats according to the American Kennel Club, and research into veterinary use of the substance is ongoing.

Moreover, scientists at Tarleton State University’s Equine Center in Texas are giving horses CBD to see whether the substance affects inflammation, stress and problematic behaviors in these animals, according to a statement from Texas A&M University. Results are expected to come out as soon as next year.

The plan at the Warsaw Zoo is to first treat Fredzia, a younger elephant who had the strongest reaction to Erna's death, according to the BBC. Researchers at the zoo have already collected feces, saliva and blood from the animals to measure their levels of cortisol, a chemical associated with stress, before the CBD trial. Scientists will keep monitoring cortisol levels in the elephants as they feed Fredzia — and eventually the other elephants — the cannabinoid, the BBC reported

Originally published on Live Science.

More than 2,700 years ago, worshipers at a "holy of holies" shrine in Israel may have gotten high on weed. Researchers discovered burnt cannabis and frankincense at the site, which was located in the Kingdom of Judah.

Researchers made the discovery after analyzing ancient residues left on two altars at the shrine. The burnt cannabis is "the first known evidence of [a] hallucinogenic substance found in the Kingdom of Judah," a region that now includes parts of the West Bank and central Israel, the researchers wrote in the study.

Once the cannabis was burned at the Iron Age site, "we can assume that the religious altered state of consciousness in this shrine was an important part of the ceremonies that took place here," study lead researcher Eran Arie, the curator of Iron Age and Persian period archaeology at the Israel Museum in Jerusalem, told Live Science in an email.

Related: Image gallery: 7 potent medicinal plants

Archaeologists first excavated the site in the 1960s; they unearthed two fortresses, dating to from the ninth to the early sixth centuries B.C., that flanked the southern border of the Kingdom of Judah. During these excavations, archaeologists found a well-preserved shrine dating to about 750 B.C. to 715 B.C. 

At the shrine's entrance were two limestone altars, one standing 18 inches (40 centimeters) high and the other 20 inches (50 cm) tall. Each altar had a shallow depression on top containing "round heaps of black solidified organic material," the researchers wrote in the study. Based on the altars' characteristics, researchers concluded this was a "holy of holies" shrine, meant to evoke the inner sanctum of the Tabernacle of the Israelites, where God was thought to appear. Tests of this black gunk in the 1960s gave mostly inconclusive results, noting only that one clump contained animal fat. 

Arie decided to reanalyze this black material, especially since some residue still remained on the altars. He teamed up with study co-researcher Dvory Namdar, a senior research fellow at the Institute of Plant Sciences at the Volcani Center of Agricultural Research in Israel. Namdar has expertise in analyzing residue from ancient burned incense, but "we never thought we [would] reveal such an amazing find" as the cannabis, Arie said. 

However, Namdar was worried that the sample could have been contaminated; at the time, she worked in a lab that conducted cannabinoid research. So, the researchers "re-sampled the altars and verified the results in another laboratory at the Hebrew University of Jerusalem," Arie said. "The results were the same."

Ceremonial burning

The new tests revealed that the smaller altar contained burned cannabis and animal droppings. It appears that "animal dung was used as the fuel [to burn] the cannabis," Arie said. Dung burns more slowly than herbs, so it would have slowed down the burning process, he said.

The taller altar contained the remnants of frankincense and animal fat, which would have promoted evaporation of the aromatic tree resin. It's the earliest evidence that frankincense was used in a cultic practice in the Kingdom of Judah, Arie said. 

Both of these findings provide clues about cultic practices in the Kingdom of Judah. In particular, the cannabis finding indicates that people may have purposefully used the plant for its "hallucinogenic ingredients," to stimulate ecstasy during cultic ceremonies, at least during the eighth century B.C., Arie said. 

Practices at this shrine may also shed light on the First Temple, also known as Solomon's Temple, which was also in the Kingdom of Judah and in use at the same time. The shrine at Arad "was an official shrine of the Kingdom of Judah," Arie said, so it's possible that these findings can be "extra-biblical evidence" that similar practices were used in the First Temple, Arie said. 

In other words, the bible mentions that frankincense was burned in the First Temple, but because this shrine used both cannabis and frankincense, these substances "were probably also (at least) part of the components of the incense that was burnt in the Temple in Jerusalem," Arie said.

Related: Photos: The ancient ruins of Shivta in southern Israel

Shopping around

Where did these burned ingredients originate? Frankincense comes from Arabia, so it's likely that the Kingdom of Judah took part in the south Arabian trade, even before the Assyrian empire encouraged such practices starting in 701 B.C., the researchers said. Moreover, it probably wasn't cheap. "The high value of frankincense is further reflected in the Bible, where its price is compared several times with that of gold and precious stones, and it is often described as a royal treasure," the researchers wrote in the study.

Cannabis, in contrast, isn't local to the Middle East. Rather, cannabis originated high on the Tibetan Plateau, according to a study of fossil pollen. What's more, there aren't any cannabis seeds or pollen remains known in the ancient Near East's archaeological record. So, it's possible that cannabis plants "may have been imported from distant origins and were transported as dried resin (commonly known as hashish)," the researchers wrote in the study. 

The new finding "is revolutionary in making a case for the use of specialized psychoactive plants in early Israelite religion," said Patrick McGovern, the scientific director of the Biomolecular Archaeology Project at the Penn Museum in Philadelphia, who was not involved in the study.

However, McGovern said the study could have delved deeper into the cannabis findings. "The proposal that the cannabis was heated to release psychoactive compounds, rather than for its aroma as an incense (provided by the frankincense, in any case), is an intriguing proposition," he said. 

It's interesting that the Hebrew Bible doesn't appear to mention cannabis use, and that there isn't any known archaeobotanical evidence for the plant at the shrine, he noted. That said, it may not be far-fetched, given that people in the Kingdom of Judah did use another mind-altering substance in rituals, namely alcohol, McGovern said. The study doesn't mention "the psychoactive properties of grape wine, which we know to have played a central role in early Israelite religion," McGovern said. 

The study was published online yesterday (May 28) in the journal Tel Aviv. 

• 25 Odd Facts About Marijuana
• 7 Ways Marijuana May Affect the Brain
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines

Originally published on Live Science.

People who are high on cannabis are more likely to form false memories, in which they wrongly "remember" information that they never actually learned or recall snippets of an event that never happened, new research suggests.

False memories can arise spontaneously when people draw faulty inferences from their actual experiences. For instance, you might remember your co-worker being at the big meeting last Monday because everyone else attended when, in reality, he was out sick. In other cases, external sources supply the misleading information that fuels false memories, whether in the form of leading questions, faulty personal accounts from other people or misinformed media coverage. 

Everyone occasionally crafts false memories, even when sober. But now, a study published Feb. 10 in the journal Proceedings of the National Academy of Sciences  suggests that cannabis use may raise the risk of forging false memories — a point that could prove critical in court. 

"The law has recognized that certain witnesses are vulnerable, so you need to take extra care" when questioning them, said co-author Elizabeth Loftus, a distinguished professor of psychological science and law at the University of California Irvine School of Law. Children and people with mental disabilities are considered "vulnerable" witnesses, for example. "Maybe cannabis-intoxicated witnesses should join that club," Loftus said. 

Two experts told Live Science that, while the effects of cannabis on memory should be taken seriously in court, more research is needed to determine when and how police should question intoxicated witnesses to obtain more reliable testimonies. 

Spontaneous confusion 

As cannabis use becomes more commonplace and widely accepted around the world, understanding how the drug affects memory will become critical to the way officials handle criminal cases, said lead author Lilian Kloft, a graduate student in the Department of Neuropsychology and Psychopharmacology at Maastricht University in the Netherlands.

"Cannabis is the most widely used drug worldwide, after legal substances such as alcohol and nicotine," Kloft told Live Science in an email. "There is a need to find out how this affects [witnesses'] memory, their reports, so that in turn evidence-based policies can be shaped." 

With this goal in mind, Kloft and her colleagues recruited 64 volunteers in the Netherlands to inhale a dose of vaporized cannabis and have their memory tested. The team designed the experiment to examine two kinds of false memories: those that arise somewhat spontaneously and those that external sources introduce. 

Related: 25 odd facts about marijuana 

To test spontaneous false memories, the team turned to a well-known experiment known as the Deese-Roediger-McDermott (DRM) Task. In that experiment, volunteers memorize a list of related words — such as "tired," "pillow," "bed" and "snore" — and then get tested on their recognition of those words. The catch is that, during the testing round, learned words get mixed in with new words that the volunteers weren't asked to memorize. In one experiment, the volunteers memorized a word list while high, and in another, they memorized a different list while sober. 

The new words ranged from totally unrelated to highly related to the words on the original list. Typically, people wrongly remember highly related words despite not having seen them before. 

Indeed, this was the case when the volunteers were tested immediately after the memorization round, whether they were high or sober. While intoxicated, however, the participants were more likely to flag somewhat related and totally unrelated words as belonging to the original list. For example, when high, people might have mistakenly said  the word "tomato" was in their original word list even if it was a sleep-themed list. 

True crime 

The results suggest that people may be particularly prone to forming spontaneous false memories while high on cannabis, especially if the misremembered details only somewhat relate to their original experience, the authors concluded. But the DRM task isn't very realistic — after all, how often are witnesses asked to memorize random words at the scene of a crime? 

To better capture a true crime scenario and examine false memories that arise from external sources, the research team used virtual reality (VR). In one simulation, the participants witnessed a fight unfolding on a train station platform, and in a second, the volunteers (while in VR) stole a handbag from someone at a bar. Half of the participants took cannabis before donning their VR gear, while the other half remained sober. 

Related: 7 ways marijuana may affect the brain

Both groups completed an interview immediately after each simulation, during which their interviewer asked leading questions laced with misinformation. For instance, a question might have wrongly implied that the attacker on the train platform wore a black coat or that he was armed with a knife. The participants also listened to a virtual co-witness give a somewhat skewed account of the event, as might happen in real life. 

When asked about true details of the virtual crimes, the sober and high groups answered the questions with similar accuracy. But when asked about details that never appeared in the simulation, the intoxicated group confirmed the inaccurate information more often than the sober group did. 

"People under the influence of cannabis show the highest risk for false memories for things or details that are poorly related to the original event," Kloft said. "It appears that [cannabis-intoxicated people] have a 'yes' bias when they are uncertain about their memory, which makes them sort of random and unreliable responders." 

Time to sober up 

The results underscore the idea that "if you question [cannabis-intoxicated] people immediately, you are going to get these false memory effects," said Manoj Doss, a postdoctoral research fellow at the Johns Hopkins Center for Psychedelics and Consciousness Research who was not involved in the study. Doss conducted a similar study using still images and written descriptions, rather than VR, and found that people who were high were more likely to falsely "remember" images they'd never seen when prompted by unfamiliar descriptions. 

But would the false memories persist after the "witnesses" sobered up? To find out, the team repeated the memory tests the following week. On the DRM task, people performed fairly similarly regardless of their state of mind during the initial experiment. If they completed the initial test while high, however, they still tended to falsely recognize unrelated words more often than their sober selves. On the VR tasks, both the sober and intoxicated groups performed similarly on the follow-up test. Presumably, these results could reflect how memory decays over time, even in sober people, Kloft said. 

"Memory decays, initially, very quickly. It declines steeply in the first 24 hours," said Annelies Vredeveldt, an associate professor in the Department of Criminal Law and Criminology at Vrije Universiteit Amsterdam and co-founder of the Amsterdam Laboratory for Legal Psychology. For this reason, it's considered best practice to interview eyewitnesses as soon as possible after a crime occurs. But in light of these new findings, the recommendation may not apply to people who are high on cannabis. 

"Probably it would be best if [cannabis-intoxicated people] were interviewed as soon as they sober up, or maybe one day after the event," Vredeveldt said. The more time that passes, however, the more their memory will deteriorate, she added. 

Although many studies have investigated the effect of alcohol on false memories, relatively few have examined how memories falter under the influence of cannabis or other popular drugs, leaving the authorities to handle intoxicated witnesses, victims and suspects without evidence-based procedures, Kloft said. "In my opinion, more research ... on other drugs and drug combinations (e.g., alcohol and cannabis) are urgently needed," she said. 

• Mixing the pot? 7 ways marijuana interacts with medicines 
• Healing herb? Marijuana could treat these 5 conditions 
• 5 pot facts for 4/20 

Originally published on Live Science. 

When the woman arrived at the emergency room, doctors thought she was having a stroke. But it turned out she was just really high. The woman was intoxicated with THC, which she had unknowingly ingested right before her symptoms started, according to a new case report.

The 64-year-old woman went to the emergency room after experiencing general weakness, mostly in her right arm and leg, according to the report, published Jan. 22 in The Journal of Emergency Medicine. Her husband also noted that her speech had suddenly changed and did not sound normal. The paramedics who brought her to the hospital had called in a "code stroke" to alert doctors of a potential stroke patient. (The code is used because stroke patients require urgent treatment with clot-busting drugs.)

The woman also said she felt odd and "apart from her body." During a physical exam, doctors noted she spoke slowly, but was able to form full sentences. She also had some weakness in her lower right leg. Doctors took some blood samples and sent her for a CT scan.

Related: 27 Oddest Medical Case Reports

The scan didn't show any signs of a stroke — there were no signs of bleeding or blockages in the brain. Other tests, including an MRI, chest X-ray and electrocardiogram (EKG), or a test of the heart's electrical activity, were also normal.

Soon, the woman said she no longer felt weak and could walk normally. Doctors canceled the stroke code and determined that she was not a candidate for emergency stroke treatment with clot-busting drugs.

But why had she reported such an odd feeling when she arrived at the hospital? Doctors asked her a few more questions about what happened. They learned that, shortly before her symptoms started, "she had eaten a cookie that was brought to their senior center social area by one of the other seniors to share," the report said. "The patient's husband noted that this person was of questionable character." 

Based on this new piece of information, doctors performed a drug test, which came back positive for tetrahydrocannabinol (THC), the active ingredient in marijuana. In other words, the woman had ingested the drug without knowing it.

THC is well known to cause certain effects on the body, including decreased concentration, altered mental state, eye redness and increased appetite. But this appears to be the first case of "focal neurologic deficits," such as weakness in the arms and legs, tied to use of THC, the authors said.

It's possible that the woman's weakness was a side effect of THC use. However, exactly how THC would cause temporary limb weakness is unclear, the authors wrote. They also noted that they cannot rule out the possibility that the woman had a ministroke, or transient ischemic attack — a stroke that typically lasts only a few minutes and doesn't cause any lasting effects. Still, if the latter were the cause, "the timing of her intoxication with a possible transient ischemic attack would be an intriguing co-occurrence," the authors wrote.

By publishing this case, the authors hope that "this knowledge will encourage physicians to consider THC intoxication as a cause of new onset extremity weakness," they concluded.

Other than a positive drug test, the woman's medical evaluation was "unremarkable," and she soon was released from the hospital, the report said.

•  25 Odd Facts About Marijuana 
•  Mixing the Pot? 7 Ways Marijuana Interacts with Medicines 
•  9 Weird Ways You Can Test Positive for Drugs 

Originally published on Live Science. 

Two newfound cannabinoids have been discovered in the glands of the Cannabis plant, and one of them may be at least 30 times as potent as the high-inducing compound THC. 

No one knows, however, exactly what effect these cannabinoids actually have on the human body.

THC, or tetrahydrocannabinol, plugs into receptors in the brain and alters our ability to reason, record memories, coordinate movements, perceive time and experience pleasure. Cannabis contains over 140 similar chemicals that interface with receptors throughout the body, but as far as we know, only THC can induce a mind-bending high. Now, scientists have uncovered two new cannabinoids, one of which structurally resembles nonpsychoactive compound CBD and the other of which looks like THC but could elicit stronger effects — at least in theory. 

The THC look-alike, named tetrahydrocannabiphorol (THCP), seems to interact with the same receptor as THC, the receptor known as CB1, according to a new study published Dec. 30 in the journal Scientific Reports. The key difference between THCP and its cousin lies in a chain of atoms jutting off the newfound compound.

Related: 25 Odd Facts About Marijuana

Research suggests that the protruding structure, called an alkyl side chain, is what allows THC to plug into its preferred receptor. A cannabinoid must carry at least three carbon rings in its side chain to gain access to CB1, and THC compounds typically carry five. On paper, a cannabinoid equipped with more than five carbon rings would fit even more snuggly into the receptor, and eight carbon rings would supply the absolute perfect fit, eliciting the strongest biological response. But no such compounds have been uncovered in nature, the authors noted in their paper.

Enter THCP. 

This compound boasts not five, not six, but seven carbon rings in its alkyl side chain. When applied to a makeshift receptor concocted in a lab dish, the compound tended to bind the substance 30 times more reliably than THC did. 

The researchers then gave THCP to lab mice and found that the animals behaved as if they were on THC, meaning their movement slowed, their temperature decreased and their reactions to painful stimuli diminished. And the animals reached this state at relatively low doses of the newfound compound; it would take about twice as much THC to induce the same effects.

Related: Mixing the Pot? 7 Ways Marijuana Interacts with Medicines

Although potent in the lab, THCP may or may not induce dramatic effects in humans, Vice reported. First of all, the compound appears to be present in plants in only small amounts, at least in the low-THC cannabis variety used by the researchers. Even assuming THCP can be grown in larger quantities, we still don’t know whether the compound would induce a high similar to that caused by its psychoactive cousin. And while THC offers some medicinal effects, including pain and nausea relief, no one knows if THCP has these qualities, Vice reported. 

In addition to THCP, the researchers also uncovered a CBD look-alike with seven carbon rings, which they named cannabidiphorol (CBDP). The team found that this compound doesn't bind strongly to either the CB1 receptor or the related receptor CB2. While CBD has been tied to anti-inflammatory, antioxidant and anti-seizure effects, investigating these effects in CBDP "does not appear to be a high priority," the authors wrote.

• Healing Herb? Marijuana Could Treat These 5 Conditions 
• 7 Ways Marijuana May Affect the Brain 
• 5 Pot Facts for 4/20 

Originally published on Live Science. 

This year saw an alarming rise in the percentage of U.S. teens who vape marijuana, according to new findings from a government-backed survey.

The trend is all the more concerning in light of the recent outbreak of vaping-related lung illnesses, which have sickened more than 2,400 people across the U.S., with the majority of cases occurring in teens and young adults, according to the Centers for Disease Control and Prevention (CDC).

The survey, called Monitoring the Future, is conducted every year to track drug use among U.S. teens and is funded by the National Institute on Drug Abuse. This year, researchers gathered data from more than 42,000 U.S. students in the eighth, 10th and 12th grades.

Results show that the percentage of 12th graders who reported vaping marijuana in the  preceding month soared from 7.5% in 2018 to 14% in 2019. This 6.5% increase is one of the largest single-year jumps seen in the survey’s 45-year history for any substance used in the previous month, the authors said. For comparison, between 2017 and 2018, the percentage of 12th graders who reported vaping marijuana in the previous month increased just 2.5%.

Among eighth graders, the percentage who reported vaping marijuana in the preceding month increased from 2.6% in 2018 to 3.9% in 2019; and among 10th graders, this percentage increased from 7.0% in 2018 to 12.6% in 2019.

The percentage of adolescents who reported vaping marijuana over the preceding 12 months in 2019 was 20% among 12th graders, 19% among 10th graders and 7% among eighth graders.

"As the number of adolescents who vape marijuana increases, so too does the scope and effect of any associated health consequences, which may include lung injury when using black market formulations," the authors, from the University of Michigan, wrote in their paper, published today (Dec. 18) in the journal JAMA.

Indeed, officials believe that vaping products containing THC, the active ingredient in marijuana, are playing a large role in the current outbreak of vaping-related lung illnesses. Around 80% of patients hospitalized with vaping-related lung illnesses reported vaping THC products. A substance known as vitamin E acetate, which is found in THC-containing vape products, has also been linked to the outbreak, according to the CDC.

"The rapid rise of marijuana vaping indicates the need for new prevention and intervention efforts aimed specifically at adolescents," the authors said.

A separate survey, also released today, similarly called attention to the rise of teen marijuana vaping. This second survey, called The National Youth Tobacco Survey, involved data from more than 38,000 U.S. students in grades 6 through 12. 

Among the entire student population, the percentage who reported ever using mairjuana in an electronic cigarette device (vaping marijuana) increased from about 11% in 2017 to nearly 15% in 2018.

The rise in marijuana vaping may be due to several factors, including the increase in sales of a newer generation of e-cigarettes known as "pod mods" that use disposable or refillable "pod" cartridges (which can include THC cartridges), according to the authors of the second paper, also published today in JAMA. Makers of this style of e-cigarette have been criticized for marketing to young people.

Other factors behind the rise in teen marijuana vaping may include increased access to marijuana through informal sources, such as friends and family members, as well as a reduced perception that marijuana can be harmful, the authors said.

More studies are needed to assess the immediate and long-term health effects of vaping marijuana, they concluded.

•  9 Weird Ways You Can Test Positive for Drugs 
•  8 Tips for Parents of Teens with Depression 
•  25 Odd Facts About Marijuana 

Originally published on Live Science. 

Young people who use marijuana frequently are more than twice as likely to have a stroke compared to those who don't use the drug at all, according to a new study. 

The findings, which will be presented next week at the annual American Heart Association (AHA) Scientific Sessions meeting in Philadelphia, add to a growing body of research linking marijuana use to an increased risk of cardiovascular problems. The new study, which will also be published in an upcoming issue of the journal Stroke, is one of the first to specifically focus on the risk of stroke in young cannabis users (under age 45).

The researchers analyzed results from a national survey, called the Behavioral Risk Factor Surveillance System, which had published data on marijuana use and stroke incidence.

Related: 7 Ways Marijuana May Affect the Brain

The authors compared the frequency of marijuana use to the incidence of stroke in people ages 18 to 44 years old. Among the 43,860 participants, 13.6% had used marijauna in the last 30 days. (The data doesn't specify the way in which participants used marijuana, though a majority of the survey respondents said they smoked it). Marijuana users tended to also report heavy drinking and use of tobacco cigarettes.

The authors found that frequent marijuana users, or people who used marijuana more than 10 days a month, but who did not use tobacco products were nearly 2.5 times more likely to have a stroke than people who did not use marijuana, according to a statement. 

For those who used marijuana frequently and also smoked cigarettes or e-cigarettes, the risk was even greater. These individuals were nearly three times more likely to have a stroke, compared with those who didn't use either marijuana or cigarettes. 

But these findings show only an association and cannot prove that marijuana use causes strokes. The authors noted that other substances, such as alcohol, may also influence the risk of stroke seen in the study, even though the scientists attempted to adjust for additional substance use in their analysis.

What's more, even if there is a cause-and-effect relationship between marijuana use and stroke, researchers don't exactly know how the drug might be leading to stroke. Marijuana use has been linked to an increased number of blood clots, which might, in turn, increase the risk of stroke, according to a previous Live Science report.

Cannabis might also trigger "reversible cerebral vasoconstriction," or a temporary narrowing of the blood vessels in the brain that has been linked with stroke, said lead author Dr. Tarang Parekh, a health policy researcher at George Mason University in Virginia. 

"In the current discussion of legalization of marijuana in the United States, we believe this study was a crucial step towards" understanding stroke risk in young marijuana users, Parekh told Live Science. "Even though cannabis is not [as] harmful or addictive as other substances, we cannot ignore its potential health risks."

A separate study, which will also be presented at the AHA meeting next week, found a link between marijuana use and an increased risk of heart arrhythmia (or rhythm problems) in young adults. The authors found that young people, or those between the ages of 15 and 34, who have cannabis-use disorder had a 47% to 52% increased risk of being hospitalized because of an arrhythmia. 

The latter study has not yet been published in a peer-reviewed journal.

• 9 Weird Ways You Can Test Positive for Drugs
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• 7 Things That May Raise Your Risk of Stroke

Originally published on Live Science.

Doctors removed a balloon full of marijuana from a man's nose — what's remarkable is that the drugs had been stuck up there for 18 years. 

The 48-year-old man had been admitted to Westmead Hospital in Sydney, Australia, after complaining of headaches, according to a report published Oct. 25 in the journal BMJ Case Reports. A CT scan of his head revealed a "firm gray mass" in his right nasal cavity, and upon questioning, the man confirmed that he had experienced recurrent nasal infections and noticed an obstruction in his nostril. 

Physicians called the mass a "rhinolith" — a term that translates to "nose stone" — meaning calcium and other minerals had built up around a "foreign body" in the man's sniffer. They pulled the plug from the patient's nostril and found that it appeared to be a "rubber capsule containing degenerate vegetable/plant matter." 

That's doctor-speak for "balloon full of weed." 

Related: 25 Odd Facts About Marijuana

Finally, the full story came out. The patient recalled an incident 18 years earlier, while he was incarcerated. During a visit, his then girlfriend snuck the man a small amount of marijuana encased in a balloon. The man put the package up his nose to conceal it from watchful prison guards.

"Despite effectively smuggling the package past the prison guards, the patient then accidentally pushed the package deeper into his nostril and mistakenly believed he had swallowed it," the doctors wrote. The balloon then went undetected in the man's nose for 18 years, until the CT scan alerted him to its presence. The minerals encasing the balloon likely helped keep its structure intact, though the doctors did not speculate as to what might have happened if the weed parcel had burst.     

"To the best of our knowledge, our case represents the first report of a prison-acquired marijuana-based rhinolith," the doctors wrote. They suspect that most drug smuggling involves someone swallowing the contraband and later passing it through their gastrointestinal tract. "Insertion into the nasal cavity for this purpose is relatively rare," they wrote.   

• 7 Ways Marijuana May Affect the Brain 
• 5 Pot Facts for 4/20 
• 27 Oddest Medical Cases 

Originally published on Live Science.

After weeks of searching for the cause of a mysterious outbreak of vaping-related lung illnesses across the U.S., health officials now say that THC-containing products may play an important role in these illnesses.

Today (Sept. 27), officials from the Centers for Disease Control and Prevention (CDC) released a new report on the outbreak showing that more than three-quarters of patients nationwide reported using vaping products containing THC, the active ingredient in marijuana. 

A second report, which focused on patients in Illinois and Wisconsin, similarly found that the vast majority of the individuals reported using THC-containing vaping products. In particular, they reported using vaping cartridges that were "prefilled" with THC, which means the cartridges were already filled and packaged before the user obtained them.

What's more, most of the patients reported obtaining the vaping products from informal sources, such as off the street or from friends or a dealer.

Still, officials stressed that they don't know for sure what's causing the outbreak, saying they can't rule out non-THC-containing products as possible risks.

"The outbreak [data] is currently pointing to a greater concern around THC-containing products," Dr. Anne Schuchat, principal deputy director of the CDC, said in a news conference today (Sept. 27). But "we do not know whether the only risky substance for lung injury is the THC-containing products."

Related: 4 Myths About E-Cigarettes

So far, the outbreak, which was first identified in July, has sickened more than 800 people in 46 states, according to the CDC. Of these, 12 people have died from vaping-related illnesses.

Many of those sickened are teens or young adults; about 62% of the cases involve 18- to 34-year-olds, and 16% of the individuals are under 18. 

Patients reported symptoms such as shortness of breath, cough and chest pain, and some reported nausea, vomiting, fever and weight loss. Most of the illnesses have been serious, with the vast majority requiring admission to the hospital and many requiring treatment in the intensive care unit.

For one of the new reports, published today in the CDC journal Morbidity and Mortality Weekly Report (MMWR), researchers analyzed information from 514 patients across the U.S. They found that 77% of patients reported using vaping products containing THC or both THC and nicotine in the month before their symptoms started. Only a small portion of patients, 16%, reported using exclusively nicotine-containing e-cigarettes.

For the second report, also published today in MMWR, state health officials in Illinois and Wisconsin conducted detailed interviews with 86 patients in the two states. In those interviews, 87% of patients reported using vaping products containing THC, and of these, nearly all (96%) were in the form of packaged, prefilled vaping cartridges.

Overall, patients reported using 87 different brands of e-cigarette products. Although no single brand was reported by all patients, two-thirds (66%) of patients reported using a brand called Dank Vapes, a black-market "brand" of vaping products. Dank Vapes doesn't appear to be a single company, but rather a branded packing used by sellers of unregulated vaping products, according to Inverse.

Officials also stressed that they don't know the exact substance causing these illnesses. Previous reports said that a substance known as vitamin E acetate, an oil derived from vitamin E, had been found in some product samples taken from patients. In addition, an analysis commissioned by NBC News found another substance, a pesticide called myclobutanil, in 10 THC vaping cartridges obtained from unlicensed dealers. This pesticide can convert into the chemical hydrogen cyanide when burned, NBC News reported.

While the investigation of the outbreak is ongoing, the CDC recommends that people consider refraining from using e-cigarette products, particularly those that contain THC.

•  9 Weird Ways You Can Test Positive for Drugs 
•  8 Tips for Parents of Teens with Depression 
•  Gasp! 11 Surprising Facts About the Respiratory System 

Originally published on Live Science. 

UPDATE: On Sept. 12, the Centers for Disease Control and Prevention (CDC) announced that there are currently 380 confirmed and probable cases of lung disease tied to vaping in 36 states. This revised case count is lower than what the agency announced last week because the new number includes only confirmed and probable cases that meet the CDC's current case definition, or the specific criteria officials use to classify a vaping-related illness. The previous case count included "possible" cases that did not necessarily meet this definition. Live Science published this article (below) on Sept. 6.

The number of Americans sickened by mysterious, vaping-related lung illnesses continues to soar as health officials unravel clues to what could be causing these illnesses.

Today (Sept. 6), the Centers for Disease Control and Prevention (CDC) announced that it is aware of 450 possible cases of severe lung illnesses tied to vaping that are under investigation in 33 states. (That's more than double the number of cases under investigation as of last week.)

Among these cases, three deaths have been confirmed in connection with these illnesses — one each in Illinois, Oregon and Indiana — and a fourth death is under investigation.

Overall, many of the patients are teens or young adults who were previously healthy. All patients reported using e-cigarettes, and many reported using the devices to vape marijuana before they got sick.

Related: 4 Myths About E-Cigarettes

So far, the cause of the illnesses is unknown; no single vaping device, product or substance has been tied to all of the cases, said Dr. Dana Meaney-Delman, the manager of the CDC's investigation into the lung illnesses.

Officials believe "chemical exposure" is likely behind these illnesses, but much more information is needed to determine which substances are involved, Meaney-Delman said at a news conference today. "[We're] working hard to understand why people are getting sick."

Yesterday, it was reported that a substance known as "vitamin E acetate" — an oil derived from vitamin E — had been found in 10 out of 18 marijuana product samples taken from patients for testing by the Food and Drug Administration (FDA). The agency is now analyzing more than 120 samples from around the country for a broad range of chemicals, said Dr. Ned Sharpless, acting FDA commissioner.

But simply identifying a compound in samples doesn't mean that it caused the illnesses, officials stressed. "Identifying any compounds present in the samples will be one piece of the puzzle but won't necessarily answer questions about causality," Sharpless said in a statement.

Today's announcement coincided with the release of several new reports on vaping-related illnesses. The reports include a detailed description of some of the cases, as well as a "case definition," or the specific criteria officials use to classify  a vaping-related illness. This will help "define the clinical picture of what we are dealing with" and help doctors identify patients more quickly, Meaney-Delman said.

One report, published today in The New England Journal of Medicine, describes a cluster of 53 patients from Wisconsin and Illinois who developed serious respiratory symptoms after vaping. Most of these patients were young — the median age was 19 — male and generally healthy prior to their illness. Patients reported symptoms such as shortness of breath, cough and chest pain, and some reported nausea, vomiting, fever and weight loss. All of the patients had vaped within the prior three months, and 84% reported vaping marijuana products.

Interestingly, the report seems to suggest that these vaping-related lung illnesses are indeed a new phenomenon, and not something that simply went undetected in the past. The rate of monthly emergency room visits for severe lung illness in young adults was twice as high in June through August 2019 than in the same months in 2018, the study found.

Another report, published Sept. 6 in the CDC journal Morbidity and Mortality Weekly Report, describes five young patients in North Carolina who had similar symptoms after vaping. All of the patients were diagnosed with lipoid pneumonia, a rare condition in which fats or oils enter the lungs and lead to pneumonia, or inflammation of the lungs. Doctors couldn't determine whether the lipids came from outside the body — from an inhaled substance — or from inside the body, due to altered fat metabolism, the CDC said.

The CDC recommends that people consider not using e-cigarettes while the investigation is ongoing. And regardless of this investigation, e-cigarettes should not be used by youth, young adults, pregnant women or adults who currently don't use tobacco products, the CDC said. What's more, people should not buy e-cigarette products off the street and should not modify the products or add substances that aren't intended for vaping by the manufacturer, the agency said.

•  9 Weird Ways You Can Test Positive for Drugs 
•  8 Tips for Parents of Teens with Depression 
•  Gasp! 11 Surprising Facts About the Respiratory System 

 Originally published on Live Science. 

 Men who smoke marijuana may have a better chance of having a baby with their female partner, compared with those who don't use the drug, a surprising new study suggests.

The study, which was published Aug. 14 in the journal Human Reproduction, involved several hundred couples undergoing fertility treatment with in vitro fertilization (IVF). The researchers found that women who reported currently using marijuana had a higher likelihood of pregnancy loss, compared with women who didn't use marijuana.

In contrast, couples whose male partner said he currently used marijuana had better chances of having a child, compared with couples whose male partner didn't currently use marijuana.

This finding was unexpected, according to the authors, from the Harvard T.H. Chan School of Public Health in Boston. The researchers had hypothesized that marijuana smoking wouldn't be related to fertility outcomes in either men or women, as has been the case in previous studies. 

Related: 25 Odd Facts About Marijuana

But the new result agrees with findings in an earlier study from the same group of researchers. In that study, men who reported ever having smoked marijuana had higher sperm counts, on average, than those who had never used the drug.

Still, the new findings don't mean that men should start smoking marijuana to boost their fertility. Only a small number of participants said they smoked marijuana around the time of their fertility treatments, which reduces the strength of the results. At most, they suggest that marijuana may not have a harmful effect on men's fertility, the authors said. On the other hand, the researchers don't think their findings should be taken as evidence that marijuana has a beneficial effect for men undergoing fertility treatment.

There is an urgent need for "additional research to clarify the role of marijuana use on human reproduction and on the offspring's health," the authors concluded.

Despite the growing use and legalization of marijuana around the world, scientists know little about how the drug impacts fertility. And few studies have included both men and women.

In the new study, the researchers analyzed information from 200 couples who underwent fertility treatment at Massachusetts General Hospital between 2005 and 2017. The researchers also included data from an additional 220 women who underwent fertility treatment, but did not have a partner in the study.

Participants were asked whether they were currently using marijuana, had used the drug in the past or had never used it.

Overall, 44% of the women and 61% of the men in the study reported they had smoked marijuana at some point in their lives. But just 12 women (3%) and 23 men (12%) in the study said they were currently using marjuana.

Among the small number of women who said they currently smoked marijuana and became pregnant during the study, more than 50% experienced a pregnancy loss, compared with just 26% of the women who were past marijuana users or who had never used the drug. 

This finding suggests that marijuana use among women "may be related to worse infertility treatment outcomes," the authors said. But they caution that since very few women in the study were current marijuana users, it's possible that this finding was due to chance.

On the other hand, among couples whose male partner was a current marijuana user, 48% eventually had a live birth, compared with just 29% of couples whose male partner was a past marijuana user or who had never used it. The link held even after the researchers took into account some factors that could affect fertility, including the participants' age, ethnicity, body mass index (BMI), tobacco smoking history, coffee intake, alcohol use and cocaine use.

More and more patients are asking about the reproductive effects of marijuana, but doctors have had few studies to share when advising patients.

"At least weekly, I have patients asking me about the effects of marijauna on male fertility," said Dr. Neel Parekh, a urologist specializing in male fertility and men's health at the Cleveland Clinic's Glickman Urological & Kidney Institute. "There just isn't a great answer we can give them yet."

In this sense, the new study is "a step in the right direction," Parekh told Live Science. 

However, the new study by itself isn't enough for doctors to recommend that men smoke marijuana prior to fertility treatment.

Parekh noted that, with only 23 men in the study reporting current use of marijuana, "It's hard to make that big of a statement saying marijuana is going to improve success rates" with fertility treatment.

But Parekh agreed with the authors that, rather than showing a benefit per se, the study suggests that smoking marijuana may not hurt the chances of success with fertility treatment when the male partner uses it.

The study authors note that their work included couples undergoing fertility treatment, and so the findings may not apply to couples trying to conceive without medical assistance. Indeed, Parekh noted that some forms of IVF use only a single sperm to fertilize an egg, and so with these treatments, a man's sperm count isn't usually a big deal. But when couples are trying to conceive naturally, sperm count matters more.

In addition, the new study only asked about marijuana smoking and not other forms of marijuana use.

More robust studies are now needed to look at this issue, said Parekh, and he expects to see more research in this area in the coming years.

•  Trying to Conceive: 10 Tips for Men 
•  Sexy Swimmers: 7 Facts About Sperm 
•  5 Myths About the Male Body 

 Originally published on Live Science. 

 A striking proportion of teens are using highly potent forms of marijuana known as marijuana concentrates, at least in one state, a new study suggests.

The study, published today (Aug. 26) in the journal Pediatrics, analyzed data from nearly 50,000 eighth, 10th and 12th graders in Arizona. The researchers found that one-third of participants said they had used marijuana, and nearly a quarter said they had used marijuana concentrates at least once in their lives.

Marijuana concentrates are substances with very high levels of THC (tetrahydrocannabinol), the active ingredient in marijuana responsible for the drug's intoxicating effects. Sometimes known as "butane hash oil," "dab," "wax," "crumble" or "shatter," these concentrates typically contain three times more THC than does the dried marijuana flower.

As more states legalize marijuana, the sale and marketing  of marijuana concentrates has skyrocketed. But few studies have examined how common the use of these products is, particularly among teens.

"It was surprising to find that so many teens had used" marijuana concentrates, study lead author Madeline Meier, an assistant professor of psychology at Arizona State University, told Live Science.

Related: 4 Myths About E-Cigarettes

The high rates of marijuana-concentrate use in teens are concerning, Meier said, because some evidence in adults suggests that using products with high-THC concentrations may increase a person's risk of psychosis, cognitive impairment and marijuana dependence .

What's more, people who are inexperienced users of marijuana concentrates, or who don't use them often — which likely comprises the majority of teen users — may be more likely to experience harmful side effects, such as loss of consciousness or burn injuries, the authors said. (Some types of marijuana concentrates are produced using flammable solvents, such as butane.)

It's important to note that the new study only included teens in Arizona, and the percentage of teens who use marijuana concentrates in other states is unknown. More studies will be needed to understand if the trend is confined to Arizona, or whether it's happening in other states as well.

The usage rates could be similar in other states that have legalized medical cannabis, as Arizona has, Meier said. However, some states have legalized medical cannabis but not marijuana concentrates, so their use might be lower in those ones, she added. It's also unclear whether states that allow recreational marijuana in addition to medical marijuana have higher rates of teen marijuana-concentrate use.

A yearly national survey known as Monitoring the Future, which looks at drug use among teens across the U.S., has also examined rates of marijuana-concentrate use to some extent. However, that survey classifies "concentrated THC" as a hallucinogen, and so only teens who report the use of hallucinogens are asked about use of concentrated THC. As a result, this type of questioning tends to underestimate use, Meier said. In 2018, the Monitoring the Future survey found that just 1.1% of 12th graders reported use of concentrated THC.

The new study also found that teens who used marijuana concentrates had much higher rates of electronic cigarette use. Indeed, teens who used marijuana concentrates were three times more likely to report using e-cigarettes, compared to those who used other forms of marijuana. (Teens are probably using e-cigarettes to vape marijuana.)

The findings come on the heels of a Centers for Disease Control and Prevention investigation of nearly 200 cases of lung disease tied to vaping. So far, investigators haven’t found a single cause for the illnesses, and do not know if all of them are related.

However, some doctors have hypothesized that the cases could be caused by a contaminant found in certain formulations of marijuana products sold for vaping, Live Science previously reported. Indeed, earlier this year, researchers described an 18-year-old who developed a lung injury after using butane hash oil daily for three years. That case report was published in the journal Respiratory Medicine Case Reports.

Meier stressed that the link between vaping and lung problems still needs to be investigated. However, some marijuana concentrates may have residual, or left over, solvents, such as butane, which can be toxic, she noted.

Further research is needed to examine if teens who use marijuana concentrates are indeed at higher risk of substance use problems and marjiuana addiction.

In addition, "as findings emerge showing high rates of concentrate use in adolescents, and increased cannabis-related risks associated with the use of high-THC cannabis, policy makers might consider putting a limit on THC concentration in cannabis," the authors concluded.

•  Mixing the Pot? 7 Ways Marijuana Interacts with Medicines 
•  9 Weird Ways You Can Test Positive for Drugs 
•  8 Tips for Parents of Teens with Depression 

 Originally published on Live Science. 

Summer is the most common season for U.S. teens and adults to try illegal or recreational drugs for the first time, a new study finds.

The study researchers analyzed information from more than 394,000 Americans ages 12 and older who completed a yearly survey on drug use between 2011 and 2017. Participants were asked whether they had used certain drugs — including LSD, marijuana, cocaine and ecstasy (also known as MDMA or molly) — and what month and year they initiated use.

During the summer (June through August), more people first tried these drugs, compared with other times of year. The findings were published today (July 23) in the Journal of General Internal Medicine. [7 Common Summer Health Concerns]

For example, 34% of people who said they'd begun using LSD in the previous two years had first tried the drug during the summer months. And among those respondents who had recently started using marijuana, cocaine or ecstasy, about 30% had initiated use during the summer. That compares with fewer than 25% of recent initiates of LSD, marijaua, cocaine or ecstasy who said they'd started using the drugs during each of the other three seasons of the year.

The researchers hypothesized that the uptick in drug initiation during the summer months may be due, in part, to people having more leisure time during the summer. Outdoor social activities, such as musical festivals, are more common in the summer and may increase a person's chances of exposure to drugs or the individual's willingness to use them, the authors wrote in the study.

"Parents and educators who are concerned about their kids need to educate them year-round about potential risks associated with drug use, but special emphasis appears to be needed before or during summer months, when rates of initiation increase," study senior author Joseph Palamar, an associate professor in the Department of Population Health at the New York University School of Medicine, said in a statement.

First-time drug users may be unfamiliar with the drugs' effects, which may put these individuals at higher risk of harm, the authors said.

Still, the problem of illegal drug use isn't going away anytime soon, and each year, millions of Americans try LSD, marijuana, cocaine or ecstasy for the first time.

People who do decide to use illegal or recreational drugs for the first time should educate themselves about the drugs' side effects, Palamar said. He also recommended having the company of trusted friends when using a drug for the first time and making sure to drink enough fluids and get enough rest to avoid dehydration, exhaustion and heat stroke.

More research is needed to determine why summer is a risk factor for drug initiation, as well as the particular situations that lead people to use drugs for the first time, the authors said.

• 6 Party Drugs That May Have Health Benefits
• 9 Weird Ways You Can Test Positive for Drugs
• Trippy Tales: The History of 8 Hallucinogens

Originally published on Live Science.

The quest for new antibiotics has led researchers to a surprising candidate: the marijuana compound CBD.

A new study finds that CBD, or cannabidiol, is "remarkably effective" at killing bacteria, at least in a test tube, the researchers in the new study said. The results showed that CBD had antibiotic effects against a number of so-called Gram-positive bacteria, including types of staph and strep bacteria, as well as strains that had become resistant to other antibiotic drugs.

Still, the results are very preliminary, and people should absolutely not self-treat infections with CBD at this time, the researchers said.

"It needs a lot more work to show [that CBD] would be useful to treat infections in humans," said study lead author Mark Blaskovich, of The University of Queensland's Institute for Molecular Bioscience's Centre for Superbug Solutions in Brisbane, Australia. "It would be very dangerous to try to treat a serious infection with cannabidiol instead of one of the tried and tested antibiotics," Blaskovich told Live Science. [6 Superbugs to Watch Out For]

The study was conducted in collaboration with Botanix Pharmaceuticals Ltd., a drug-discovery company that's investigating uses of synthetic cannabidiol for a range of skin conditions. The company also helped fund the study.

The work will be presented today (June 23) in San Francisco at ASM Microbe, the annual meeting of the American Society for Microbiology; the research has not yet been published in a peer-reviewed journal.

New antibiotic?

CBD has garnered a lot of attention in recent years for its potential to provide therapeutic effects without producing the high typically associated with marijuana. But so far, the Food and Drug Administration (FDA) has approved CBD only in prescription-drug form for treating rare types of childhood epilepsy.

In addition, studies suggest that CBD may have anti-inflammatory effects, but whether it also has antibiotic effects has been unclear.

In the new study, the researchers tested whether a synthetically produced form of CBD could kill different types of bacteria.

In experiments in lab dishes, the synthetic CBD did just as well as the prescription antibiotics vancomycin and daptomycin in killing certain strains of Staphylococcus and Streptococcus bacteria. The compound even worked against strains of staph and strep bacteria that had become resistant to vancomycin and daptomycin, the authors said.

CBD also showed activity against bacterial biofilms, which form when bacteria secrete proteins to form films on surfaces. These biofilms can cause difficult-to-treat infections.

Future work

Experts cautioned that many different compounds appear to show antibiotic effects in lab dishes, known as "in vitro" experiments, but these findings don't always translate to people.

"Just because [CBD] has antibiotic activity in an in vitro assay doesn't mean it does in the human body," said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, who wasn't involved with the study. "Lots of different compounds … have [antibiotic] activity in a petri dish."

Many more studies will be needed to see if CBD could be used as an antibiotic in people. Research will need to determine the dose needed to kill bacteria in the body, whether this dose is safe and how the antibiotic might be delivered, Adalja said.

Still, Adalja said the research is promising. "[It's] more evidence that there [are] a lot of untapped avenues of research with CBD," he said.

The authors now plan to conduct animal studies to understand the types of infections CBD might treat, as well as how CBD may kill bacteria, Blaskovich said. In addition, Botanix plans to conduct a clinical trial in people to test whether CBD can effectively remove Staphylococcus aureus bacteria on the skin before surgeries, to prevent post-surgical infections, he said.

• 27 Devastating Infectious Diseases
• 25 Odd Facts About Marijuana
• 9 Weird Ways You Can Test Positive for Drugs

Originally published on Live Science.

Getting high on marijuana may not be a modern pastime, as archaeologists have found the earliest clear evidence to date that people were smoking cannabis for its psychoactive properties some 2,500 years ago.

They found evidence of burned cannabis with high levels of tetrahydrocannabinol (THC) (the cannabis ingredient responsible for the high) on 10 wooden incense burners, known as braziers; the burners were found alongside eight human burials at an ancient site known as Jirzankal Cemetery (also called Quman Cemetery) on the Pamir Plateau of western China.

The burners all carried a mystery residue, which a chemical test soon revealed to be cannabis. "To our excitement, we identified the biomarkers of [cannabis]," study co-researcher Yimin Yang, a professor in the department of archaeology and anthropology at the University of Chinese Academy of Sciences, told reporters at a news conference. [25 Odd Facts About Marijuana]

Researchers have known for decades that ancient people in eastern China cultivated cannabis as long ago as 3500 B.C. But this cannabis was grown as an oil-seed and fiber crop, and so it had low psychoactive properties. In other words, the ancient people harvesting cannabis for these purposes probably weren't smoking or ingesting it for its high.

The cannabis residues found in the braziers, however, tell another story. It's likely that ancient people purposefully selected cannabis plants with high THC levels and then smoked them as part of a ritual or religious activity associated with these burials, "perhaps, for example, aimed at communicating with the divine or the deceased," the researchers wrote in the study.

Ancient cemetery

Archaeologists began excavating Jirzankal Cemetery in 2013, and were intrigued to find the braziers, which held heating stones. To determine what these ancient people had burned, the archaeologists partnered with Yang's team, which used a technique known as gas chromatography mass spectrometry (GC/MS) to analyze the chemical residues on the braziers.

In the first test, the researchers found biomarkers of cannabis on the internal charred wood of a brazier. Then, they analyzed an ancient sample of cannabis from the 2,500-year-old Jiayi Cemetery in Turpan, China, where the plant was found laid across a man's chest as a burial shroud. This test showed preserved components of cannabis, including cannabinol (CBN), cannabidiol (CBD) and cannabicyclol (CBL).

While THC does not preserve well, CBN is a good indicator that it's present. Intriguingly, the researchers found ample CBN on the wooden braziers and on two of the stones, indicating that its THC levels were higher than those typically found in wild plants. As a control, they tested samples from the outside of the braziers, but didn't find any cannabinoids.

Of note, the burials are more in line with the ancient mortuary practices from ancient Central Asia, including the modern-day countries of Uzbekistan and Kyrgyzstan, than they are from China, the researchers said.

Where did the psychoactive pot come from?

Most wild cannabis, as well as early cultivated varieties of the plant, contain low levels of psychoactive compounds. So where did this high-THC variety come from?

The researchers have two main ideas. Perhaps a wild variety of pot with high psychoactive levels arose naturally, and then humans found and cultivated it. "I agree that humans are always going to be looking for wild plants that can have effects on the human body, especially psychoactive effects," study co-researcher Robert Spengler, the laboratory director at the Max Planck Institute for the Science of Human History in Germany, told reporters. [7 Ways Marijuana May Affect the Brain]

How did cannabis with high THC levels come about? Given that Jirzankal Cemetery is high up in the mountains — more than 9,800 feet (3,000 meters) above sea level — perhaps the plants encountered stressors there that led them to create more psychoactive properties, the researchers said.

In this line of thinking, the extreme mountain environment — such as low temperatures, low nutrient availability, high exposure to ultraviolet rays and strong light intensity — may have caused the plants to change how they produced or metabolized certain compounds, which could lead to the creation of greater amounts of psychoactive compounds, the researchers said.

"This is potentially linking these plants — the plants with higher THC production — to higher elevation," Spengler said. "But that's all fairly theoretical, so we really cannot pinpoint exactly what the mechanisms for the higher THC level are."

Another idea is that humans — either intentionally or inadvertently — played a role in increasing the plant's psychoactive properties. Perhaps people bred different marijuana plants that led to varieties with higher THC levels.

"Some of them may have been rapidly domesticated by humans simply moving them or transporting them [along trade routes such as the silk road] … from the Caucasus all the way to East Asia," Spengler said. "So, it's possible that humans were still inflicting evolutionary changes on these plants without actually intensively cultivating them."

That said, it's still an "open debate" whether the psychoactive pot occurred naturally, or whether humans played a role, he said.

The study is the latest to look at cannabis's origins and historic uses. In May, another group of researchers posited that the cannabis plant likely originated high on the Tibetan Plateau, according to an analysis of fossil pollen. The new finding "provides yet another piece in the biomolecular archaeological puzzle of the 'abiding mystery of Central Asia' and its impact on human cultural and biological development through the millennia," Patrick McGovern, the scientific director of the Biomolecular Archaeology Project at the Penn Museum in Philadelphia, who was not involved in the study, told Live Science. "Much more remains to be learned."

The study was published online today (June 12) in the journal Science Advances.

• 9 Weird Ways You Can Test Positive for Drugs
• 7 Ways Marijuana Interacts with Medicines
• Marijuana Could Treat These Five Conditions

Originally published on Live Science.

The popularity of medical marijuana is soaring, and among the numerous products consumers are seeking are CBD, or cannabis oils.

A wealth of marketing material, blogs and anecdotes claim that CBD oils can cure whatever ails you, even cancer. But the limited research doesn't suggest that cannabis oil should take the place of conventional medication, except for in two very rare forms of epilepsy (and even then, it's recommended only as a last-resort treatment). And, experts caution that because CBD oil and other cannabis-based products are not regulated or tested for safety by the government or any third-party agency, it's difficult for consumers to know exactly what they're getting.

What is CBD?

Simply put, cannabis oil is the concentrated liquid extract of the marijuana plant, Cannabis sativa.

Similar to other herbal extracts, the chemicals in cannabis oils vary depending on how the extract is made and what chemicals were in the plant to begin with.   

Cannabis plants produce thousands of compounds but the most well recognized belong to a class called cannabinoids. There are several cannabinoids but the two that are most well-known among consumers are THC (tetrahydrocannabinol) and CBD (cannabidiol).

THC is the primary psychoactive compound in marijuana and it is what people are searching for when they want a product that gives them a "high." Unlike THC, CBD isn't known to cause psychoactive effects, and is therefore attractive to those who want to avoid the high but who believe there are other benefits of CBD, said Sara Ward, a pharmacologist at Temple University in Philadelphia. [Healing Herb? Marijuana Could Treat These 5 Conditions]

CBD products that don't contain THC fall outside the scope of the U.S. Drug Enforcement Agency's (DEA) Controlled Substances Act, which means CBD products are legal to sell and consume as long as they don't have THC. That's likely one of the reasons why CBD products, including CBD oil, are becoming more socially acceptable and increasingly popular. In 2016, Forbes reported that CBD products are expected to be a $2.2 billion industry by 2020.

How are CBD oils consumed?

The physiological effects of cannabinoids can vary widely from person to person, and also depend on how they're consumed. That lack of predictability is one of the reasons why cannabis oil is a challenging candidate for developing into a medicine, Ward told Live Science.

"Two people may eat a brownie [made with cannabis oil] and one may absorb massive amounts of cannabinoids and the other may not," Ward said. "How long it takes to work and how long it stays in the system differs greatly."

It's a little more uniform when the product is absorbed by smoking or vaping the oil, Ward said. But, "there are obvious concerns about smoking something." A 2007 review published in the journal JAMA Internal Medicine found that smoking marijuana resulted in similar declines in respiratory system health as smoking tobacco. A similar review published in 2014 in The American Journal of Cardiology found that marijuana smoke inhalation can increase the chances of heart attack or stroke. Neither review analyzed the effects of vaping cannabis oil alone, so it's unclear if it has the same health risks as smoking other marijuana products.

Why do people use cannabis oil?

People claim that cannabis oil can be used to treat a wide range of conditions, though evidence to back up these claims is often lacking. For example, according to Medical News Today, people use cannabis oil for conditions ranging from pain to acne; some even claim the oil can cure diseases like Alzheimer's and cancer. (But again, there is no clinical evidence to support these claims.) 

A review published in 2017 in the journal Frontiers in Pharmacology described how CBD may work to protect the hippocampus — the part of the brain responsible for several important functions, such as learning, memory and navigation — during times of stress, and may also help prevent brain-cell destruction that results from schizophrenia. Another 2017 review published in the journal Annals of Palliative Medicine summarized a handful of studies that suggest cannabis oils containing THC or CBD, or both, may help with chronic pain management, but the mechanism is unclear.

Cannabis treatment in people with certain forms of epilepsy has been more promising. The only FDA-approved cannabis-based drug is Epidiolex, a CBD oral solution for treating two rare and severe forms of epilepsy. A recent clinical trial found that Epidiolex reduced convulsive seizures by 50% in children with Dravet syndrome, a type of epilepsy, MedPage Today reported. 

Why medical experts are hesitant about CBD

It's important to know that the research in this area is in its infancy, partly because we haven't really understood much about CBD until relatively recently," said Marcel Bonn-Miller, an adjunct assistant professor at the University of Pennsylvania Perelman School of Medicine. He pointed out that the classification of marijuana as a Schedule 1 drug by the DEA makes it difficult to get material to use in laboratory studies. Schedule 1 drugs have a high potential for abuse, according to the DEA, and are illegal under federal law.

Because of this classification, it's not easy for researchers to get their hands on the drug. "That's not to say you can't do it, but there are hoops you need to jump through that can be a pain, which may deter researchers from going into this space," Bonn-Miller said. "Relatively speaking, it's a small group of people in the U.S. that do research on cannabinoids in humans."

However, Bonn-Miller told Live Science that he thinks cannabis research is on the upswing. "If we flash forward five years I think you'll see more studies," he said. Those studies could reveal more conditions that CBD may be helpful for and may also reveal that some of the reasons why people say they use CBD oil are not supported by the science but are instead a placebo effect. "And that's why we need to do the studies," he said.  

The side effects and risks involved with consuming marijuana-based products aren't clear, either, Bonn-Miller said. It's important to "determine cannabinoids that are useful therapeutically while understanding and using cannabinoids that are associated with less risk," he said. At least with CBD, he said, it doesn't appear to have the potential for addiction. That's different from THC, which has been associated with addiction, he said, and negative side effects, including acute anxiety.

What consumers should know

Both Bonn-Miller and Ward stress that it's up to the consumer to be well-educated about the material they're purchasing and the research that's out there. "The companies that are creating [cannabis oils] are offering lots of claims about its use that are not necessarily substantiated by any research," Bonn-Miller said. So "I think there needs to be, from a consumer standpoint, a lot of vigilance," he added.

And the products on the shelf aren't all the same, Ward said. "There can be many, many different varieties, and if you're thinking about doing this for medical reasons, you want to find a trusted source and do your research," she said. "Where does that oil come from, and how confident can you be that you know the exact percentages of the different cannabinoids in the product?"

Bonn-Miller also explained that it's imperative to exhaust the traditional and established front-line treatments that are available before seeking out these products. "CBD is not really a first-line treatment for anything," he said. "You don’t want situations where somebody says, 'I have cancer I'm going to forgo chemotherapy because I read something about CBD or THC helping with cancer.'" That's not a good idea, Bonn-Miller said. "Not only is the science not there, but you may end up worse off."

Original article on Live Science.

The marijuana compound CBD, or cannabidiol, may help reduce drug cravings in people with heroin addiction, a preliminary new study suggests.

The study, which is published today (May 21) in the American Journal of Psychiatry, involved 42 people with heroin-use disorder who were attempting to abstain from the drug.

Participants visited the laboratory and were shown "cues" intended to trigger a drug craving — in this case, videos of people using heroin, or objects involved in drug use, like syringes. (Seeing these types of "cues," in an uncontrolled setting, can contribute to drug relapse, the authors said.) Before their lab session, participants received either a dose of CBD or a placebo.

Participants who received CBD reported experiencing lower drug cravings in response to the cues, as well as lower anxiety, compared with those who received a placebo. What's more, the effects appeared to be somewhat durable, lasting up to a week after participants took CBD. [Mixing the Pot? 7 Ways Marijuana Interacts with Medicines]

Still, the results are far from definitive — the researchers did not examine whether CBD actually prevents drug-relapse outside of a laboratory setting, and so future studies are needed to answer this question.

But the new findings suggest that "CBD holds significant promise for treating individuals with heroin use disorder," study lead author Yasmin Hurd, director of the Addiction Institute at the Icahn School of Medicine at Mount Sinai in New York, said in a statement.

CBD has received a lot of attention in recent years for its potential to have therapeutic effects without producing the "high" typically associated with marijuana. But so far, the Food and Drug Administration (FDA) has only approved CBD in prescription-drug form for treating rare types of childhood epilepsy.

Hurd stressed that self-treatment with CBD for opioid use disorder is not advised at this time, and might even be harmful given that non-prescription forms of CBD are not regulated. "A lot of CBD that is available to the public…[has] inaccurate information as to what is actually in the container, and may even be contaminated with toxins," Hurd told Live Science.

The study was funded in part by GW Pharmaceuticals, which makes the FDA-approved form of CBD.

'Urgent need' for treatments

Currently, most drug treatments for opioid use disorder act on opioid receptors, and thus come with their own addiction risk. As a result, they are tightly regulated by the government. In light of the opioid epidemic, there is an "urgent need" to develop treatments for opioid addiction that do not act on opioid receptors, the authors wrote in the study.

Previously, Hurd and colleagues studied CBD in animal models, and found that CBD reduced heroin-seeking behavior in the animals in response to "cues" intended to trigger a craving. The researchers also conducted early studies in people to determine that CBD is safe to take together with opioids.

In the new study, the 42 participants were randomly assigned to one of three groups, which took 400 milligrams of CBD once daily, 800 mg of CBD once daily, or a placebo once daily, for three consecutive days. (Participants in the CBD groups received Epidiolex, the FDA-approved prescription drug.) The study was "double blind," meaning that neither the researchers nor the subjects knew whether they had received CBD or a placebo.

After participants took their dose of CBD or placebo, they were exposed to heroin-related "cues;" and later watched a "neutral" video showing relaxing scenarios, such as scenes of nature.

As expected, participants reported higher cravings after viewing the heroin-related cues compared with the neutral videos. But if participants received CBD before their session, their cravings were significantly reduced compared with those who received a placebo, the study found.

The researchers also saw reductions in anxiety, as well as physiological measures, including heart rate and levels of the "stress hormone" cortisol, in the CBD group compared with the placebo group.

The effects were seen as soon as 1 hour after the CBD dose, and up to one week later. The latter finding suggests that CBD may still have an anti-craving effect when little to no trace of the substance remain in people's systems, the authors said.

Future research

Dr. Harshal Kirane, director of Addiction Services at Northwell Health's Staten Island University Hospital, called the work "a step in a very encouraging direction," and applauded the effort to scientifically evaluate the effects of CBD.

However, Kirane said the study had some important limitations. Since it was a small study, the results need to be replicated in a larger group of people, he said.

And although the study found that CBD reduced cravings in the laboratory, it did not reduce self-reported cravings outside of the laboratory as measured by a take-home questionnaire.

"That raises some concerns as to what the actual real-world application of CBD could be" for these patients, Kirane told Live Science. Studies also need to evaluate the long-term effects of CBD for these patients, beyond one week, he said.

Future research should examine whether CBD may work as a supplement to current therapies for opioid use disorder to enhance their effects, Kirane said. Indeed, Hurd told Live Science that one of the next steps of the research is to study CBD as an adjunct therapy to current medications, such as methadone or buprenorphine.

• 10 Interesting Facts About Heroin
• 9 Weird Ways You Can Test Positive for Drugs
• Healing Herb? Marijuana May Help Treat These 5 Conditions

Originally published on Live Science.

Synthetic marijuana, made from chemicals sprayed onto plant material, can have a range of effects and is thought to be more dangerous than natural marijuana. The drug, which is sometimes referred to as K2 or spice, has been linked to serious side effects, such as seizures and psychosis.

But it's difficult to predict how synthetic marijuana will affect users, so a group of researchers in the Netherlands tested the substance's effects on 17 healthy volunteers in the lab. Their findings were published March 14 in the journal Cannabis and Cannabinoid Research.

The participants came to the lab twice, seven days apart. During one visit, they were given a synthetic cannabinoid called JWH-018 that was mixed with hemp, and during another visit, they were given a placebo (in this case, just hemp, with no synthetic marijuana mixed in). During each visit, the participants were not told which compound they were receiving. [7 Ways Marijuana May Affect the Brain]

Five of the participants were given a fixed dose of the synthetic marijuana, with the amount based on their body weight, and the remaining 12 received variable amounts.

After the participants inhaled the vapors of either compound, the researchers monitored them for 12 hours. During this time, the researchers took the people's vitals, tested their cognitive performance and had the participants periodically report how they were feeling.

Results showed that the synthetic cannabinoid increased heart rate within the first hour of smoking and significantly impaired memory. But there was a huge variation in how people reported feeling, with only about half of the participants reporting feeling "high." There was also a big variation in the amount of the substance that ended up in people's bloodstreams.

"We think that's due to our way of administration, which was [in and of itself] a challenge," said lead study author Eef Theunissen, a researcher in neuropsychopharmacology at Maastricht University in the Netherlands.

To administer the compounds, the researchers created their own glass pipe that heated up the substance, and the participants then inhaled the resulting vapor through an attached plastic piece. When the researchers analyzed the air tube after the study, they found that there was some residue left over. In addition, some of the vapor could have escaped, so some people could have inhaled less.

But this is similar to "what happens in real life," Theunissen told Live Science. "People inhale [the drug] in different ways, and the amount that they inhale is very unpredictable."

The people who reported feeling high performed worse in tests measuring reaction time than those who didn't report feeling high. (That first group also performed worse on these tests compared to people who took the placebo.) In addition, people who reported feeling high had higher levels of confusion, amnesia and dissociation, among other symptoms, compared with those who didn't report feeling high.

Ultimately, the dose of the drug given was a lot lower than what's been reported in overdose cases. That led Theunissen and her team to conclude that the serious side effects that are often seen in overdoses are probably due to higher doses of the drugs or a combination of different synthetic cannabinoids.

JWH-018 is "one of the old" synthetic cannabinoids and it's not as popular anymore, Theunissen said. It's been replaced by newer, more potent compounds, and so the results are likely an "underestimation of what's happening on the streets," she added.

Part of the problem with synthetic cannabinoids is that there are so many, Theunissen said. Indeed, Live Science previously reported that there are thousands of synthetic cannabinoids on the market, and more are constantly being synthesized. When one specific compound is made illegal, manufacturers tweak the structure slightly so that the substance isn't covered by laws or can't be detected in drug tests.

Though the results of the new study can't really be translated to what's happening on the streets, "we had to start somewhere," Theunissen said.

This was the first experiment that studied synthetic cannabis in a controlled setting, and Theunissen said she hopes it'll be a good jumping-off point for other studies, such as those comparing the synthetic drug's effects to those of pot.

• 25 Odd Facts About Marijuana
• Marijuana Could Treat These 5 Conditions
• 9 Weird Ways You Can Test Positive for Drugs

Originally published on Live Science.

People who use marijuana on a daily basis may be at increased risk for developing psychosis, particularly if they use high-potency marijuana, a new study from Europe suggests.

The study analyzed information from more than 1,200 people without psychosis living in 10 European cities and one city in Brazil, and compared them with 900 people living in those same cities who were diagnosed for the first time with psychosis. (Psychosis means a person experiences a loss of touch with reality.)

The researchers found that people who reported using marijuana daily were three times more likely to have a diagnosis of first-episode psychosis, compared with people who reported never using the drug. What's more, those who reported using high-potency marijuana on a daily basis were five times more likely to have a diagnosis of first-episode psychosis, compared with those who never used it. [25 Odd Facts About Marijuana]

In addition, the study is the first to suggest that the pattern of marijuana use in a given area may contribute to the rate of psychosis in the population. For example, in Amsterdam, where high-potency cannabis is widely available, those who reported using high-potency cannabis on a daily basis were nine times more likely to develop psychosis, compared with those who didn't use marijuana. (In the U.S., high-potency marijuana is also much more common today than several decades ago.)

"As the legal status of cannabis changes in many countries and states, and as we consider the medicinal properties of some types of cannabis, it is of vital public health importance that we also consider the potential adverse effects that are associated with daily cannabis use, especially high-potency varieties," lead study author Dr. Marta Di Forti, of the Institute of Psychiatry, Psychology, & Neuroscience at King's College London, said in a statement.

Still, it's important to note that the study found only an association, and cannot prove that using marijuana actually causes psychosis.

The study was published yesterday (March 19) in the journal The Lancet Psychiatry.

Marijuana and psychosis

Previous studies have suggested a link between heavy marijuana use and an increased risk of psychosis. But these studies couldn't determine how this link affected rates of psychosis in the general population.

In the new study, the researchers found that about 30 percent of patients with psychosis reported daily marijuana use, compared with just 7 percent of controls (people without psychosis); and 37 percent of patients reported high-potency marijuana use, compared with 19 percent of controls.

The study also found that the rate of cannabis use among the controls in a given location was linked with the rate of psychosis in that location. So the more people who used the drug daily; and the more who used high-potency marijuana, the higher the rate of psychosis.

The researchers estimate that, overall, about one in five new cases (20 percent) of psychosis across the 11 study cities may be linked to daily marijuana use; and one in 10 new cases of psychosis (12 percent) may be linked to the use of high-potency marijuana.

Future research

The new study is "in line with a lot of research over the last few years showing an association between use of marijuana … and onset of psychotic illness," said Dr. David Roane, chairman of psychiatry at Lenox Hill Hospital in New York City, who was not involved with the study. It's "increasingly evident that [marijuana use is] a risk factor" for psychosis, Roane told Live Science.

Still, the new study cannot rule out "reverse causation," meaning it could be that people with psychosis are more likely to use marijuana than people without the mental health condition, according to Suzanne Gage, of the University of Liverpool's Department of Psychological Sciences, who wrote a commentary accompanying the article. Even though the study included people who were diagnosed with their first episode of psychosis, they may have experienced less severe symptoms prior to their diagnosis, Gage noted.

Future research should aim to identify people whose use of marijuana could put them at particularly high risk for psychosis, Roane said.

In the meantime, Roane recommends that people be aware of the scientific link between marijuana use and psychosis. "It might be one of the strongest reasons to consider delaying use of marijuana," smoking less frequently, avoiding high-potency marijuana or avoiding marijuana entirely, he said.

• 9 Weird Ways You Can Test Positive for Drugs
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• 5 Conditions Marijuana Could Help Treat

Originally published on Live Science.

The marijuana compound CBD, or cannabinol, is surging in popularity in the wellness community, for its alleged health benefits, without the high normally associated with pot. But a new study suggests that marijuana’s main active ingredient, THC (tetrahydrocannabinol) — the one that gives users a high — may be more responsible for the plant's therapeutic effects.

The researchers looked at data from more than 3,000 people who had tried marijuana to relieve medical symptoms. These participants had all tracked their marijuana use with an app on their smartphones.

The study found that higher THC levels were strongly linked with reported symptom relief. In contrast, levels of CBD were not linked with symptom relief. [25 Odd Facts About Marijuana]

"Despite the conventional wisdom… that only CBD has medical benefits while THC merely makes one high, our results suggest that THC may be more important than CBD in generating therapeutic benefits," study co-author Jacob Miguel Vigil, associate professor in the Department of Psychology at the University of New Mexico (UNM), said in a statement.

The study was published Feb. 25 in the journal Scientific Reports. It was funded by the University of New Mexico Medical Cannabis Research Fund, which takes donations from the public and the cannabis industry. Three of the study authors are employed by MoreBetter Ltd., the company that makes the cannabis tracking app used in the study.

The researchers noted that the study had several limitations — for example, the data was self-reported, and the study lacked a control group that didn't use cannabis. Users may also have experienced a placebo effect, in which they expected certain products (such as those with higher THC, which tend to be more expensive) to work better.

Still, the study is one of the first to examine, in real time, which marijuana properties are linked with reported benefits. Given the increasing popularity of medical cannabis, the researchers call for more studies to better guide patients about the dosage, effectiveness and safety of medical marijuana products.

Cannabis app

Because marijuana is still illegal in the U.S. at the federal level, research on the real-time effects of medical cannabis has been limited.

In the new study, the researchers took advantage of data from the Releaf App, which aims to help people track their marijuana use and learn what types of marijuana products seem to work best for their symptoms. The app asked users for information such as the strain of marijuana and the levels of THC and CBD.

Participants reportedly took marijuana for a range of symptoms, including depression, anxiety, insomnia, stress, fatigue and back pain. The participants reported the severity of their symptoms on a scale of 0 (no symptoms) to 10 (severe symptoms) before using marijuana, and then again within the next 90 minutes after taking the drug.

On average, participants experienced a 3.5 point decrease in symptom severity on the 11-point scale.

Out of all the recorded marijuana characteristics, THC levels were the most strongly tied to reported symptom relief. THC levels were also tied to both negative side effects (such as "dry mouth" and "feeling foggy") and positive side effects (such as feeling "relaxed" and "peaceful"). CBD levels were generally not linked with reported symptom relief or side effects.

The researchers noted that, even though CBD content is reported on marijuana product labels, the labels may not be accurate — with one study finding that CBD content can be inflated on product labels. If that's the case, CBD may not have been linked with symptom relief because the dose was too low to have an effect. It could also be that CBD has more latent effects, and the 90-minute window used in the study wasn't long enough to capture these effects, the researchers said.

CBD hype?

The new study is "very interesting," said Dr. Donald Abrams, an integrative oncologist at the University of California San Francisco's Osher Center for Integrative Medicine, who has studied marijuana and was not involved in the current study.

Abrams noted that, other than studies on CBD for epilepsy in children, there's limited evidence on CBD's effects. "Everybody's espousing CBD for wellness," Abrams told Live Science. "I just think it's gotten a little bit out of proportion to the evidence."

Abrams agreed with the authors about the challenges of studying cannabis-based treatments, particularly given the numerous products that are commercially available. But "using an app like they did here is a good approach to collect sizable amounts of data."

He added that while "this sort of research doesn't provide the strongest evidence… it gives us avenues to pursue further, in perhaps randomized clinical trials," which are considered the gold standard for medical research.

• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• 9 Weird Ways You Can Test Positive for Drugs
• 7 Ways Marijuana May Affect the Brain

Originally published on Live Science.

American views on marijuana have shifted incredibly rapidly. Thirty years ago, marijuana legalization seemed like a lost cause. In 1988, only 24 percent of Americans supported legalization.

But steadily, the nation began to liberalize. By 2018, 66 percent of U.S. residents offered their approval, transforming marijuana legalization from a libertarian fantasy into a mainstream cause. Many state laws have changed as well. Over the last quarter-century, 10 states have legalized recreational marijuana, while 22 states have legalized medical marijuana.

So why has public opinion changed dramatically in favor of legalization? In a study published this February, we examined a range of possible reasons, finding that the media likely had the greatest influence.

It's not about use, geography or demographics

Our study ruled out a few obvious possibilities.

For one, it's not about marijuana use. Yes, marijuana use has increased. Data from the National Survey on Drug Use and Health show that, in 2002, about 10 percent of adults reported using marijuana the previous year. By 2015, 13.5 percent reported using. But that increase is too small to have had much of an impact on attitudes.

And it's not about older, more conservative Americans being replaced by younger generations who are more familiar with marijuana. Both younger and older people developed more liberal views about the legalization of marijuana at a similar pace over the last 30 years. In this way, changes in attitudes about marijuana legalization mirror recent increases in support for LGBTQ individuals.

We looked to see if people who lived in states where it was illegal, but resided next to ones where it became legal, were more likely to have changed their views. But the rate of change has been no different in states that legalized marijuana than in others.

Likewise, the pace of change has been similar across political parties, religions, educational levels, racial and ethnic groups and gender. As politically polarized as the country may seem, when it comes to marijuana, Americans have been changing their attitudes together, as a nation.

We did find that a small part of the increase in support was related to more people disaffiliating with religion. The proportion of people who do not identify with a religion has increased some, by about 7 percent between 2007 and 2014. People who do not have a religion tend to be more liberal than others. However, this factor accounts for only a small proportion of the change.

Media medical framing

So what's going on? What has likely made the biggest difference is how the media has portrayed marijuana. Support for legalization began to increase shortly after the news media began to frame marijuana as a medical issue.

We took The New York Times as a case study, looking at the number of published articles from 1983 to 2015 about marijuana. Just before the number of Americans supporting legalization began to increase, we found a sharp increase in the proportion of articles about marijuana that discussed its medical uses.

In the 1980s, the vast majority of New York Times stories about marijuana were about drug trafficking and abuse or other Schedule I drugs. At that time, The New York Times was more likely to lump marijuana together in a kind of unholy trinity with cocaine and heroin in discussions about drug smuggling, drug dealers and the like.

During the 1990s, stories discussing marijuana in criminal terms became less prevalent. Meanwhile, the number of articles discussing the medical uses of marijuana slowly increased. By the late 1990s, marijuana was rarely discussed in the context of drug trafficking and drug abuse. And marijuana had lost its association with other Schedule I drugs like cocaine and heroin in the New York Times. Gradually, the stereotypical persona of the marijuana user shifted from the stoned slacker wanting to get high to the aging boomer seeking pain relief.

Of course, many Americans do not read The New York Times. But analysis of newspapers of record, like this one, provide insight into how the news media has changed its framing of marijuana, especially during an era when newspapers were still a primary news source.

Harsh criminal justice system

As Americans became more supportive of marijuana legalization, they also increasingly told survey researchers that the criminal justice system was too harsh.

In the late 1980s, the "war on drugs" and sentencing reform laws put a large number of young men, often black and Latino, behind bars for lengthy periods of time. As Americans started to feel the full social and economic effects of tough-on-crime initiatives, they reconsidered the problems with criminalizing marijuana.

Because support for the legalization of marijuana and concerns about the harshness of the criminal justice system changed at about the same time, it's difficult to know what came first. Did concern about the harshness of the criminal justice system affect support for legalization — or vice versa?

By contrast, the cause and effect is clearer with respect to the media framing of marijuana. The news media's portrayal of marijuana began to change shortly before the public did, suggesting that the media influenced support for the legalization of marijuana.

Once attitudes begin to change, it is difficult to know what keeps the momentum moving. Whatever the initial impetus, attitudes today are drastically more supportive, and legalization is increasing fast.

Amy Adamczyk, Professor of Sociology and Criminal Justice, City University of New York; Christopher Thomas, Ph.D Candidate in Criminal Justice, John Jay College of Criminal Justice, and Jacob Felson, Associate Professor of Sociology, William Paterson University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A marijuana lollipop with a very high dose of the drug's active ingredient tetrahydrocannabinol (THC) may have triggered a man's heart attack, according to a new report of the man's case.

The 70-year-old man decided to try edible marijuana to see if it would reduce the pain from his osteoarthritis and help him sleep. The man had smoked some marijuana in his youth, but had never tried an edible product, according to the report, which was published today (Feb. 11) in the Canadian Journal of Cardiology.

One night, the man consumed nearly an entire marijuana lollipop, which contained a staggering 90 milligrams of THC, more than 12 times the dose in a typical joint.

Within a half hour, the man experienced "fearful hallucinations," followed by "crushing chest pain," the report said.

The man was taken to the hospital, where doctors determined that he had had a heart attack. The patient had a known history of heart disease, but he was taking several medications for his condition, and had not experienced a heart problem for more than two years. [25 Odd Facts About Marijuana]

It appears that the large dose of THC placed a "sudden and unexpected strain" on the man's body that may have triggered his heart attack, the report's authors wrote. The high dose led to hallucinations and anxiety, which in turn increased his heart rate, blood pressure and levels of the stress hormone catecholamine, all of which are known to have harmful effects on the heart, they wrote.

With the increased legalization of marijuana — the drug is now legal for recreational uses in Canada and several U.S. states — the report's authors say people should be aware that marijuana, like all drugs, may sometimes pose health risks.

"Marijuana can be a useful tool for many patients, especially for pain and nausea relief," lead case report author Dr. Alexandra Saunders, of Dalhousie University's Internal Medicine Program in New Brunswick, Canada said in a statement. "At the same time, like all other medications, it does carry risk and side effects."

The authors called for more research into how different formulations of marijuana may affect the cardiovascular system, particularly among the aging population.

Marijuana and heart problems

The new case is just one of multiple reports linking marijuana use to heart problems. For example, in 2014, doctors reported the case of a young man in the United Kingdom who also had a heart attack after smoking marijuana. Larger studies have also linked marijuana to a higher risk of stroke and heart failure.

Still, a review study published last year concluded that there is currently not enough scientific evidence available to determine marijuana's effect on the risk of heart problems.

In an editorial accompanying the study, Dr. Neal Benowitz, a professor of medicine at the University of California, San Francisco, wrote that marijuana might pose heart risks in three ways: Through the inhalation of smoke from marijuana, through the direct effect of THC on the cardiovascular system, or through indirect effects of THC related to anxiety and hallucinations, as in the current case.

So what should doctors recommend for people with heart disease who want to use cannabis products? Benowitz said there isn't evidence available to answer this question. But he said that for patients with heart disease who want to use marijuana, he would recommend products that contain only the compound cannabidiol (CBD), which does not have psychoactive effects like THC. And if patients want to use marijuana for the effects of THC, Benowitz said he would advise patients not to smoke the products (to reduce exposure to smoke), and would recommend the smallest dose that produces the desired benefit.

Benowitz noted that some edible products may contain multiple "servings" of THC, as was the case with the patient's marijuana lollipop. In this case, just a few licks of the 90 mg THC lollipop might have provided an appropriate starting dose, he said.

"Understanding appropriate dosing would likely have prevented the toxicity suffered by the patient," Benowitz wrote. "Patients may need counseling as to what constitutes a low dose, and how that compares with the amount of THC in products they may have purchased," he concluded.

Shortly after his heart attack, the man said he had trouble doing some daily tasks and wasn't able to exert himself as much as before. His doctors advised him not to consume such a high dose of THC in the future.

• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• 9 New Ways to Keep Your Heart Healthy
• 7 Ways Marijuana May Affect the Brain

Originally published on Live Science.

Men who smoke marijuana may have higher sperm counts than those who have never used the drug, a surprising new study suggests.

The findings are "not consistent" with previous research, which has suggested that marijuana has a harmful effect on men's testicular function, the researchers said.

However, the study, published in the Feb. 6 issue of the journal Human Reproduction, doesn't mean men should start smoking pot to up their sperm counts.

The findings are far from conclusive, and more research is needed to understand whether smoking marijuana could indeed, at certain levels, have a positive effect on sperm production.

But the study does highlight how little researchers know about the effects of marijuana on reproductive health, study senior author Dr. Jorge Chavarro, an associate professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health in Boston, said in a statement. "We know a lot less than we think we know." [25 Odd Facts About Marijuana]

Marijuana and sperm

Previous studies had suggested that smoking marijuana may lower a man's sperm count, especially among heavy users. For example, in 2015, researchers from Denmark found that men who smoked marijuana more than once per week had sperm counts that were nearly 30 percent lower than those who didn't smoke marijuana, or those who used the drug less frequently.

However, the effects of more moderate marijuana use on sperm counts among men is less clear.

In the new study, the researchers analyzed information from 662 men who, along with their partners, were evaluated for infertility from 2000 to 2017 at the Massachusetts General Hospital Fertility Center. The men answered survey questions about how often they smoked marijuana or used other drugs, and they also provided sperm and blood samples.

Overall, a little over half of the men (55 percent) reported ever smoking marijuana in their lifetimes, and 11 percent said that they currently smoked marijuana.

The researchers found that men who reported ever having smoked marijuana had an average sperm concentration of 63 million sperm per milliliter of semen, compared with 45 million sperm per milliliter of semen among those who had never used marijuana. The findings held even after the researchers took into account some factors that could have affected sperm concentration, such as age, cigarette smoking and alcohol use.

What's more, only 5 percent of the marijuana smokers had lower-than-normal sperm concentrations — that is, lower than 15 million sperm per milliliter of semen. Among men who never smoked marijuana, 12 percent had lower-than-normal sperm concentrations.

Among men who had ever smoked marijuana, those who used it more often had higher testosterone levels than those who used it less often.

Interestingly, each additional year that had passed since a man last used marijuana was tied to a slight increase in sperm count.

"Our findings were contrary to what we hypothesized at the start of the study," study lead author Feiby Nassan, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health, said in the statement.

But the study can be interpreted in several ways. It may be that low or moderate levels of marijuana use have a beneficial effect on sperm production, but heavier use reverses this effect. Or, it could also be that men with higher testosterone levels are more likely to engage in "risky" behaviors such as drug use; and the researchers found the link between marijuana and sperm count "because men with higher testosterone, within normal levels, have higher sperm counts and are more likely to smoke cannabis," Nassan said.

Jury still out

It's known that moderate- to heavy-use of tobacco or alcohol is tied to lower sperm counts, but whether marijuana has the same effect is up for debate, said Dr. Sarah Vij, a urologist at the Cleveland Clinic who was not involved with the study.

Vij said she applauded the study authors for looking at this question, since it is a topic that needs more research.

But the new study doesn't provide a conclusive answer. "Overall, the jury is still out on how marijuana impacts a man's fertility potential," Vij told Live Science.

Vij pointed out that both marijuana users and nonusers in the study had normal sperm counts, on average. So the study can't draw any conclusions about whether marijuana use is tied to better fertility.

In addition, it takes about three months for men to undergo a full cycle of sperm production to produce mature sperm. This means that using marijuana years ago "really should not have any impact at all on [a man's] current fertility state," Vij said.

And yet, the study still found that men who said they used marijuana at least a year ago had higher sperm counts than men who used it more recently. Vij said she wondered if "there's something that goes along with marijuana use" that's tied to better sperm production.

The researchers also noted that their study was conducted among men who visited a fertility clinic, and so the results may not necessarily apply to the general population. In addition, men in the study self-reported their marijuana use, and it's possible that some participants were not truthful about their marijuana use, due to the social stigma or illegal status of the drug in Massachusetts at the time the data was collected.

• Sexy Swimmers: 7 Facts About Sperm
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• 5 Myths About the Male Body

Originally published on Live Science.

Smoking pot just once might be linked to changes in young brains, a new study suggests.

Adolescents who smoked marijuana one or two times had increased amounts of gray matter — a combination of neuron bodies and cells that feed them — in their brains compared with those who hadn't, according to a new study published yesterday (Jan. 14) in the Journal of Neuroscience.

A bigger brain volume may sound like a benefit for adolescents, but it may not be, said lead study author Catherine Orr, a lecturer in the department of psychological sciences at Swinburne University of Technology in Australia. [7 Ways Marijuana May Affect the Brain]

That's because, in adolescence, the brain typically undergoes a process called pruning, Orr said. During this process, which goes on through a person's early 20s, the brain chips away at its existing gray matter, and increases the amount of white matter, which consists of the long tails of neurons called axons that connect cells, and their protective coating called myelin.

Though it’s not absolutely clear why the brain does this, the best explanation to date is that the process makes the brain more efficient, cutting away unnecessary or redundant components, and also makes the brain more complex by building more connections, Orr said.

That's why interfering in the process — by adding more gray matter — could potentially be a bad thing.

Measuring gray matter

In their study, Orr and her team looked at brain scans from 46 teens, all age 14, from Ireland, France, England and Germany. Some reported having smoked marijuana once or twice while others reported never having used the drug at all. The researchers controlled for other factors such as cigarette smoking and alcohol-use that could have also driven these changes.

The study found that those who smoked pot had higher volumes of gray matter in areas of the brain that had cannabinoid receptors, compared with those who reported never using the drug. Compounds in marijuana bond to cannabinoid receptors, which are found in areas including the amygdala (which is involved in emotion and threat processing), the hippocampus (which is involved in memory and learning), and the nucleus accumbens (which is involved in reward and addiction).

The researchers also found that those who had increased gray matter in their brains also had lower perceptual reasoning and a lower ability to perform a task quickly than those with normal levels of gray matter

"I personally was surprised at how extensive the effects were," Orr told Live Science.

Previous studies had found marijuana affects similar areas of the brain, however, these studies have had inconsistent results. For example, some studies in adults have found that marijuana-use was linked to an increase in gray matter, while others found the opposite. Orr noted that because these earlier mostly looked at adult brains, it's difficult to untangle the potential effects of other substances such as alcohol.

Even so, increasing evidence shows that adults that use marijuana at higher rates or for longer amounts of time or those who started earlier in life showed greater changes in the brain, she said.

Still, Orr said that more research is needed to say for sure what the effects of marijuana are on the brain. The small sample size of the study makes it difficult to disentangle the effects that other activities may also have on the brain, she added.

It's also unclear whether these changes in the brain are long-lasting, Orr said, adding that it would be good to do a follow-up study to explore this question. Ultimately, the researchers hope to be able to "identify which people are more at risk of these brain-based effects and [let] people know what [these effects] are," Orr said.

• Marijuana Could Treat These 5 Conditions
• 25 Odd Facts About Marijuana
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines

Originally published on Live Science.

Recreational marijuana use is becoming increasingly legal across the U.S., but that doesn't mean that it's safe. As with alcohol and tobacco, the drug comes with risks. And a new study finds regular marijuana may — similar to alcohol and tobacco — affect a man's sperm count and vitality.

While the study was small — just 24 participants — researchers found, for the first time, that higher concentrations of tetrahydrocannabinol (THC) in urine corresponded to a lower sperm count. (THC is the compound in marijuana responsible for the drug's high.) The study also found that pot smokers had changes in their sperm genetic profile that, in other studies, have been associated with abnormal growth and cancer.

The study, which was published today (Dec. 19) in the journal Epigenetics, could not determine whether these changes in sperm quantity and quality could affect the fertilization process and the health of the offspring, but the researchers advise caution nonetheless. [25 Odd Facts About Marijuana]

"In the absence of a larger, definitive study, the best advice would be to assume these changes are going to be there [in sperm]," said lead author Susan Murphy, the chief of the Division of Reproductive Sciences in the Department of Obstetrics and Gynecology at Duke University Medical Center in North Carolina. "I would say, as a precaution, stop using cannabis for at least six months before trying to conceive."

Previous studies have hinted that smoking marijuana can lower sperm count, that is, the number of sperm in semen when ejaculated. The new study, however, is the first to show a strong correlation between THC concentrations in urine and the number of viable sperm. On average, the sperm concentration in the semen of the 12 non-smokers in the study was about twice as high as it was in the 12 smokers, the study revealed.

More worrisome for the researchers was the degree of epigenetic changes among pot smokers. Epigenetics refers to the suite of small chemical "tags" that are added to the DNA structure and regulate gene expression. While this is a normal process, it can be altered by environmental exposures.

The researchers found that the men who smoked marijuana had epigenetic changes in their sperm DNA involving hundreds of genes and two important regulatory pathways: one for helping bodily organs reach their full size; the other for basic growth during development. Several kinds of cancer are associated with the interference of these pathways, though this study did not find a specific link between marijuana use and cancer.

As with sperm count, the higher the concentration of THC in the men's urine, the more pronounced the epigenetic changes to their sperm were. The research group's corresponding study on rats revealed a similar pattern in the same group of genes.

"We don't yet know what that means, but the fact that more and more young males of child-bearing age have legal access to cannabis is something we should be thinking about," senior study author Scott Kollins, a professor in psychiatry and behavioral sciences, also at Duke, said in a statement.

Changes in sperm quantity and quality induced by marijuana smoking might not be permanent, Murphy told Live Science. Men generate new sperm daily. Sperm take about 70 days to mature and then, if not ejaculated, will die shortly after that and be reabsorbed into the body.

"The sperm DNA… is not mutated in the traditional sense" by marijuana, Murphy said. "By definition, epigenetic alterations can affect gene regulation without changing the DNA sequence.

This means that, in the absence of marijuana use, new sperm may be able to develop normally. Nevertheless, damaged sperm from marijuana use could theoretically adversely affect the offspring, "assuming that said sperm is viable, capable of fertilization and results in a viable embryo," Murphy added.

Tim Jenkins, an epigenetics and male fertility expert at the University of Utah School of Medicine, who was not involved in the study, told Live Science that "despite the limited sample size in this study, a real strength are the animal data which comport remarkably well with the human data," which "makes the results significantly more convincing."

However, Jenkins stressed the importance of addition research. "It is imperative that additional work is performed in this realm to identify the real risk of cannabis use on sperm function but most importantly, on offspring health," he said. "This study represents a great first step in that effort, but there is still a great deal of work that is required.”

For their next study, Murphy said they'd like to at least double the sample size to improve the statistical significance of the results.

• Trying to Conceive: 12 Tips for Men
• 7 Ways Marijuana May Affect the Brain 
• Marijuana Could Treat These 5 Conditions

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.

Scientists have proved that inhaling vaporized marijuana will get you, like, way higher than smoking the exact same amount of weed.

The new research, led by scientists at the Johns Hopkins Behavioral Pharmacology Research Unit in Baltimore, tested the effects of smoked versus vaped marijuana on 17 participants who had smoked marijuana before, though not in the 30 days before the study's start (participants had smoked once in the last year, on average). Over the course of six 8.5-hour sessions, these participants got very, very high for science.

The study was funded by the Substance Abuse and Mental Health Services Administration, though one of the study's authors reported that he has previously received fees from, or consulted for, companies with ties to cannabis. [25 Odd Facts About Marijuana]

During each session, participants either smoked or vaped a dose of marijuana containing 0 milligrams, 10mg or 25mg of tetrahydrocannabinol (THC) — the primary psychoactive component in cannabis. While each participant ended up both smoking and vaping all three possible doses over their six sessions, they were blind to how much THC they were consuming each time. The participants were kept in the dark in order to prevent bias while filling out a subsequent drug-impairment questionnaire — which, as every pot enthusiast knows, is the most fun thing you can do while super-high.

In addition to self-reporting how stoned they felt via questionnaire, participants were also subjected to a battery of physical and cognitive tests throughout the duration of each high. The stoners had their heart rates and blood pressures measured 10 times over 8 hours, and were asked to complete computerized tasks that involved replicating shapes on a screen, solving simple addition equations and responding to two different stimuli simultaneously with a mouse and a computer keyboard. Again: The apex of weed-enabled fun.

The results of these tests showed that, first of all, inhaling a 25mg dose of THC will get you really, really high, regardless of whether it was smoked or vaped. (After taking this dosage, two participants vomited, and another experienced hallucinations.) Likewise, for both smokers and vapers the majority of drug effects — including high heart rate, dry mouth, red eyes, paranoia and the munchies — peaked within the first hour after getting high, and sometimes did not return to baseline levels for more than 8 hours. (Often, these effects persisted for hours after the participants' blood THC concentration returned to normal.)

Overall, the effects of vaping proved much more potent at every dosage.

"Vaporized cannabis produced significantly greater subjective drug effects, cognitive and psychomotor impairment, and higher blood THC concentrations than the same doses of smoked cannabis," the researchers wrote in their study, published today (Nov. 30) in the journal JAMA Network Open.

At both the high and low doses, vaped weed resulted in significantly higher concentrations of THC in participants' blood than smoked weed. And the vapers made roughly twice as many mistakes on the cognitive tests and felt greater negative drug effects, including dry mouth, itchy eyes and paranoia, than the smokers did.

Simply put: Vaporized weed got people higher. And, according to the researchers, their doses weren't even that strong compared to what's commercially available.

"Notably, the highest dose of cannabis administered in this study (25mg of THC: 0.19 g; 13.4 percent THC) is substantially smaller and has a lower THC concentration than what is typically contained in pre-rolled cannabis cigarettes available for purchase in cannabis dispensaries, which commonly contain roughly 1.0 g of cannabis with THC concentrations often exceeding 18 percent," the study authors wrote.

With recreational weed now legal in nine American states and all throughout Canada, it's important to remember that even moderate amounts of THC can have significant impairing effects on casual consumers, and that not all methods of consuming cannabis are created equal.

• 7 Ways Marijuana May Affect the Brain
• Mixing the Pot? 7 Ways Marijuana Interacts with Medicines
• Why Do People Vape? Reasons Have Changed

Originally published on Live Science.

Sorry to break it to you, but you can't get high off hemp. The plant responsible for the ropey bracelets kids make at summer camp produces only trace amounts of the high-inducing compound, THC, or tetrahydrocannabinol. Indeed, these trace amounts of THC are some of the main characteristics that distinguish hemp from its cannabis relative, marijuana.

Still, it's not all bad for hemp: The plant produces another lucrative compound called CBD, or cannabidiol. This nonpsychoactive molecule is the key ingredient in the first-ever cannabis-based drug approved by the Food and Drug Administration. Called Epidiolex, the drug is used to treat rare forms of epilepsy in children.

What's more, widespread beliefs about CBD's other potential benefits have helped build up a $202 million market for hemp oil containing the molecule. [25 Odd Facts About Marijuana]

But how did we end up with these two molecules in the first place?

A team of geneticists, biologists and botanists teamed up to find out. Together, they analyzed the genomes of one hemp and one marijuana strain, publishing the results Monday (Nov. 26) in the journal Genome Research.

This isn't the first time some members of this research team has tried to map out the genomes of the two plants. They previously attempted to do so in 2011, said co-study author Harm van Bakel, a geneticist at the Icahn School of Medicine at Mount Sinai in New York. (Van Bakel does not have ties to any cannabis companies, however, some of his co-authors do.) Back then, the team found that the plants' genomes were full of small pieces of DNA that repeated themselves back to back in several regions of the genetic code.

These repeated chunks don't behave like plant DNA; instead, they behave like viruses, in that they can replicate and insert themselves all over the genome, van Bakel said. This virus-like behavior suggests that these segments may have originally descended from viruses that once infected the plants. What's more, these repeating segments are responsible for the overall length of many plant and animal genomes. In hemp and marijuana, he noted, the segments make up 73 percent of the DNA.

New and improved technology

But the analysis tool the team used in 2011 cut the genome into pieces that were too small, making aligning the segments difficult — many of the pieces started and ended with identical repeat segments.

This time around, the research group used an analysis method that mapped out larger chunks of genome. "That was enough to reconstruct a much more contiguous and less fragmented version of the genome," van Bakel told Live Science. The scientists also crossbred the hemp with the marijuana, because the hybrid's genome formed a more complete map of the parents' chromosomes. [10 Amazing Things Scientists Just Did with CRISPR]

These genetic maps showed that the THC and CBD genes are located in slightly different spots on the two genomes but that those genes share a genetic ancestor — one gene that, sometime in the past, duplicated and allowed two new versions, THC and CBD, to develop. The researchers also found that the replicating segments that behave like viruses (and likely were viruses, long ago) wound up in and around the THC and CBD genes, and helped create the duplication event that allowed the genes to evolve into what we have today. And, surprise: The team found a third, similar gene that codes for a molecule called CBC, or cannabichromene, which also appears in hemp and marijuana.

Still, more research is needed to pin down when these divergences in the THC and CBD genes happened and what the ancestral gene looked like, said van Bakel. Those studies will include all other available hemp and marijuana varieties, because both are constantly being bred to produce specific levels of THC and CBD. With a better understanding of how we got these two beneficial genes, farmers may be able to skip the time-consuming breeding process and instead plant varieties they know will create the compounds they want. For example, CBC dampens some THC effects, so nailing the right ratio of the two molecules is important, van Bakel said.

For most other U.S. crops, genome maps exist, as either a draft or something detailed, van Bakel noted. "Cannabis is in the middle of that pack, more towards the end still," he said. Van Bakel, along with his colleagues and other geneticists, plans to keep going — and with the rate the THC and CBD industry is growing, these scientists have some catching up to do.

• Marijuana Could Treat These Five Conditions
• 7 Ways Marijuana Might Affect the Brain
• 7 Ways Marijuana Interacts with Medicines

Editor's note: This story was updated on Nov. 29 to correct Harm van Bakel's affiliation (he is no longer with the University of Toronto) and clarify several points about how the virus-like segments help the plant's gene evolve into what we have today.

Originally published on Live Science.

A woman who frequently ended up in the hospital with intense bouts of vomiting turned out to have a mysterious syndrome tied to heavy marijuana use, according to a new report of the case.

The 27-year-old woman had been hospitalized six times in the last year with episodes of severe vomiting, according to the report, by Dr. Umesh Sharma, chair of the Division of Community Hospital Medicine at the Mayo Clinic in Rochester, Minnesota. The woman reported experiencing nausea, vomiting and abdominal pain for two days prior to her most recent hospitalization. She described the pain as "squeezing" in her abdomen, along with a "bruised and sore" feeling in her back, the report said.

She told doctors that she had smoked marijuana since she was 20 and that over the last year, she had used the drug almost every day, according to the report, which was published Oct. 14 in the journal BMJ Case Reports.

Doctors considered several possible causes for her symptoms, including that she might have a stomach bug or a condition that causes inflammation in the abdominal organs, or she could be pregnant. However, test results, including a recent CT scan of her abdomen, came back normal, and she had a negative pregnancy test. [25 Odd Facts About Marijuana]

But her symptoms also fit those of a little-understood condition called cannabinoid hyperemesis syndrome. People with this condition are heavy marijuana users who have recurring bouts of severe nausea, vomiting and abdominal pain. Curiously, many people with the condition report that taking hot showers relieves their symptoms. And indeed, in this case, the woman said that hot showers seemed to temporarily relieve her symptoms.

The condition was first recognized in 2004, but U.S. doctors have reported seeing it more frequently in recent years. However, exactly what causes this condition and why hot showers help with the symptoms are not known. It's also unclear why only some marijuana users develop this condition.

But doctors do know that long-term use of drugs can result in changes in the brain and the nervous system, Dr. Kennon Heard, a toxicologist at the UCHealth University of Colorado Hospital, told Live Science in an April interview. In addition, doctors know that endogenous cannabinoids — compounds in the body similar to those found in marijuana — are integral to the body's pain system, said Heard, who was not involved in the woman's case.

One possible explanation for the condition is that long-term stimulation from the ingredient in marijuana that produces the drug's high — called tetrahydrocannabinol (THC) — alters the body's pain system in a way that results in the symptoms of cannabinoid hyperemesis syndrome.

If this is the case, hot showers may help to relieve symptoms by stimulating a different sensory signal that distracts the body from the pain signal, Heard said.

In the new report, the patient also received topical capsaicin, a medical cream or lotion that contains the  active ingredient capsaicin, which is derived from chili peppers. Capsaicin activates receptors in the body that sense heat and pain, and prolonged activation of these receptors is thought to reduce sensations of pain, according to the National Institutes of Health. The medicine helped relieve the woman's abdominal and back pain.

Although there's still much to learn about cannabinoid hyperemesis syndrome, it appears that quitting marijuana can, in many cases, cure the condition. Indeed, the patient in the new report was counseled about the possible side effects of heavy marijuana use, and she decided to stop using the drug. The patient's condition improved, and she left the hospital four days later, the report said.

Originally published on Live Science.