Could Marijuana Use Make Injuries More Painful?

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Marijuana use may affect how much pain people feel and the dose of painkillers they need following a traumatic injury, such as an injury from a car accident, a new study suggests.

The study found that, after experiencing a traumatic injury, marijuana users reported higher levels of pain, and needed higher doses of opioid painkillers, compared with patients who didn't use marijuana.

The researchers stressed that the findings are preliminary, and more studies are needed to confirm the results. But if the results are confirmed, the study could have implications for treating pain in marijuana users — a population that may be growing due to increased legalization of the drug, the researchers said. [Mixing the Pot? 7 Ways Marijuana Interacts with Medicines]

The findings suggest "marijuana users in need of pain control deserve special consideration when selecting the dosage and frequency of narcotics [painkillers]," said study lead author Kristin Salottolo, a clinical epidemiologist at the Swedish Medical Center's Trauma Research Department in Englewood, Colorado.

 The study was published June 19 in the journal Patient Safety in Surgery.

Marijuana and pain

The researchers started the study after treating trauma patients in Colorado who used marijuana routinely, and "were noted to have poor pain control and required higher than normal amount of narcotics," Salottolo told Live Science. "We wanted to see if this anecdotal observation held up" in a scientific study, she said.

The study researchers analyzed information from about 260 people who were involved in motor vehicle accidents between January and April 2016 and who were admitted to trauma centers in Colorado and Texas.

Of these patients, 21 percent (54 patients) reported using marijuana recently or tested positive for marijuana on a drug test, and 6 percent (16 patients) reported daily or near-daily marijuana use. (Marijuana use was reported four times more frequently in Colorado, where the drug is legal for medical and recreational purposes, compared with Texas, where the drug is illegal for both purposes.)

About 9 percent of participants tested positive for prescription or "street" drugs other than marijuana, including amphetamines, barbiturates, benzodiazepines, cocaine, methamphetamine and opiates.

Patients who used marijuana but not other drugs consumed 7.6 milligrams of opioid medications a day while in the hospital, on average, compared with 5.6 milligrams for patients who didn't use marijuana or other drugs.

What's more, when asked to report their level of pain on a scale of 0 to 10 (with 0 being the lowest pain and 10 being the worst), marijuana users had a daily pain score of 4.9, on average, compared with 4.2 for non-marijuana users.

These effects were less pronounced in patients who used other drugs in addition to marijuana, the study found.

More awareness

Dr. Anne Wagner, medical director of the UCHealth Burn Center in Aurora, Colorado, who was not involved in the study, agreed with the findings. Wagner and her colleagues have also conducted research on burn patients that found that those who are heavy marijuana users require "much higher doses of opioids" compared with patients who don't use marijuana.

Using higher doses of narcotics to control pain can lead to many other problems — for example, it means that marijuana users frequently end up with longer hospital stays than non-marijuana users, because "we don't want to discharge them on massive doses of narcotics," Wagner told Live Science. In addition, marijuana users may experience marijuana withdrawal, including symptoms of nausea and vomiting, which, in turn, could prevent them from getting proper nutrition and interfere with healing, Wagner said.

The findings may seem surprising at first, because some studies suggest that marijuana use can help with certain types of pain, such as chronic pain. But Wagner noted that the marijuana helps only if patients can take it, and because the drug is still illegal at the federal level, hospitals typically cannot allow patients to take it.

Wagner said more work is needed to figure out how to best treat trauma patients who are marijuana users, including whether a drug called dronabinol, which contains a synthetic form of tetrahydrocannabinol (THC), can help with symptoms of marijuana withdrawal, and what dose of this drug works best.

Wagner added that more awareness is needed about the potential effects of marijuana on trauma patients. "I really think a lot of people think [marijuana is] very harmless," Wagner said. "I don't think they're at all aware about … how much it's going to affect them in their recovery" from injury, Wagner said.

The study researchers noted that their findings are limited in part because the study was relatively small, and was retrospective, meaning it analyzed data that was collected previously. The researchers are planning a larger study that follows patients forward in time to further investigate the link between marijuana use and pain and opioid use in trauma patients.

Editor’s note: This story was updated on June 19 to include quotes from the study author.

Original article on Live Science.

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.