What Is CBD Oil, and Does It Really Work?
Concentrated liquid extracts from marijuana plants are becoming more and more popular as alternative medicine, but the science isn't there.
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The popularity of medical marijuana is soaring, and among the numerous products consumers are seeking are cannabis oils — the most in-demand of which is referred to simply as CBD oil.

A wealth of marketing material, blogs and anecdotes claim that cannabis 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 cannabis 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.

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.

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.

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.

"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.

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.