In recent years, health professionals and policymakers have become increasingly interested in medical cannabis’s potential to reduce opioid use and prevent overdose deaths. Several states have already added opioid replacement provisions to their medical marijuana programs or approved opioid use disorder as a qualifying condition. At the same time, studies and surveys have seemed to suggest that states with legalized medical marijuana were seeing fewer opioid-related overdose deaths. But a new study, published yesterday, is complicating our understanding of whether legalization could be a potential solution to the opioid epidemic.
In 2014, researchers found that states with legal medical cannabis access showed a trend of declining opioid overdose mortality rates over a period of about 10 years from 1999 to 2010. In medical marijuana states, patients were filling fewer opioid prescriptions. And fewer people were dying from opioid-related overdose deaths.
The study kicked off of wave of policy shifts approving medical cannabis as a treatment for opioid use disorder. More studies came out that seemed to corroborate the 2014 paper, showing how legal marijuana of any kind seemed to reduce opioid-related harm.
But a new study, published yesterday in the Proceeding of the National Academy of Sciences, says those gains are disappearing. The paper, titled “Association between medical cannabis laws and opioid overdose mortality has reversed over time,” points out a dramatic swing in the association between medical marijuana legalization and opioid overdose deaths.
Where once legal medical marijuana states had a 21 percent lower rate of opioid deaths than states without medical marijuana, those same states now have a 23 percent higher rate of opioid deaths than prohibition states. In other words, cannabis is losing the battle against opioids.
So the negative association between opioid deaths and legalized medical marijuana observed between 1999 and 2010 didn’t last. And from 2010 to 2017, it actually reversed. “What we found was that association between enacting a medical cannabis law and the rate of deaths from opioid overdose actually reversed over time,” said the study’s lead author, Chelsea Shover, a postdoctoral research fellow at Stanford University.
So why isn’t legal medical marijuana having the same effect on opioid death rates as it once did? Was it ever the real cause behind declining overdose rates? Researchers don’t yet have all the answers. But they have some hypotheses. Shover says the decrease in opioid-related deaths in medical marijuana states may have something to do with their average wealth. Patients in Alaska, California, Colorado, Oregon and Washington may simply have been able to afford better access to addiction treatment and medications.
Then, there’s the view that medical cannabis use is still relatively uncommon, and therefore unable to really make an impact on the opioid epidemic. “We find it unlikely that medical cannabis—used by about 2.5 percent of the US population—has exerted large conflicting effects on opioid mortality,” the study’s authors wrote. “A more plausible interpretation is that this association is spurious.”
But just because claims about cannabis’s potential to fight the opioid epidemic should be met with skepticism, doesn’t mean we shouldn’t research how it could. “Research into the therapeutic potential of cannabis should continue,” the study says.
Indeed, that research is already too promising not to continue pursuing. It may be hard to show how marijuana laws are impacting opioid mortality rates. But cannabis-based medicines and therapies have already shown promise as effective treatments for addiction. One recent study, for example, found that cannabidiol (CBD) helps reduce cravings and abstinence anxiety in people struggling to overcome opioid and heroin use disorders.