By Roger Chriss, PNN Columnist

Medical cannabis legalization isn’t helping reduce opioid overdoses. Two major studies have closely examined over a decade’s worth of data, finding no support for the idea that legalizing medical cannabis reduces prescription opioid use, overdose or mortality.

In June, Stanford researchers led by Chelsea Shover, PhD, published a study in PNAS using the same methodology as a 2014 JAMA study that found a positive association between cannabis legalization and lower opioid mortality from 1999 to 2010. But Shover and colleagues included more recent data and states with legalized medical cannabis.

“Our expanded analysis does not support the interpretation that broader access to cannabis is associated with lower opioid overdose mortality,” they concluded.

The 2014 study was very cautious in its findings, but cannabis advocates and industry representatives used it to support legalization efforts.

“It’s become such a pervasive idea,” Shover told STAT News. “It would be amazing if it was this simple, but the evidence is telling us now that it’s not.”

Early this month, Columbia University’s Mailman School of Public Health published a new study in JAMA Network Open that looked at whether people use cannabis in place of prescription opioids.  Researchers looked at data from 627,000 people aged 12 years and older who took the National Survey on Drug Use and Health from 2004 to 2014.

The results showed that enactment of medical marijuana laws was not associated with a reduction in prescription opioid abuse, contradicting the hypothesis that people would substitute marijuana for prescription opioids.

“We tested this relationship and found no evidence that the passage of medical marijuana laws — even in states with dispensaries — was associated with a decrease in individual opioid use of prescription opioids for nonmedical purposes," said senior author Silvia Martins, MD, PhD, an associate professor of epidemiology at Columbia.

The Shover-PNAS study also made the important point that medical cannabis users comprise only about 2.5% of the U.S. population. The vast majority of cannabis use is recreational. The Washington State Liquor Control and Cannabis Board estimates that only about 20% of so-called medical users are really using cannabis for medical reasons.

In other words, there aren’t enough medical cannabis users to impact nationwide overdose trends. And in state-level analysis, there is no evidence of any substantial effect, positive or negative, from medical cannabis legalization.

There are concerns that cannabis could actually make the opioid crisis worse. A 2018 study published in the American Journal of Psychiatry found that “cannabis use appears to increase rather than decrease the risk of developing nonmedical prescription opioid use and opioid use disorder.”

"My main concern is by basically misinforming potential patients about the supposedly beneficial effects of cannabis, they may forgo a treatment that is lifesaving," NIDA director Nora Volkow, MD, told USA Today. “Scientific evidence does not support claims that marijuana helps people kick opioids.”

The FDA is taking note, warning a large cannabis operator last week to stop making unsubstantiated claims that its products can treat chronic pain, cancer, opioid withdrawal and other medical conditions.

Medical cannabis has uses, of course, but taking it for conditions it is not proven to help may lead to harms. Perhaps a way can be found to incorporate cannabis in addiction treatment, but that is quite different from expecting medical cannabis legalization to be an exit ramp for the opioid crisis.

Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.

The information in this column should not be considered as professional medical advice, diagnosis or treatment. It is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.