STANFORD, Calif. — Medical marijuana may provide help to people battling ailments from glaucoma to epilepsy, but when it comes to slowing the opioid epidemic, it’s not preventing people from using — despite prior research showing otherwise. According to a new study out of the Stanford University School of Medicine, there is no evidence of a connection between a reduction in deaths from opioid overdoses and the availability of medical cannabis in states where it’s legal.

These findings contradict a 2014 study that legalization advocates, public officials, and some physicians have pointed to as a reason to legalize the drug. That study, which looked at data from 1996 through 2010, found lower rates of fatal opioid overdoses in the medical marijuana states than in states that haven’t legalized cannabis in any form.

“If you think opening a bunch of dispensaries is going to reduce opioid deaths, you’ll be disappointed,” says study co-author Keith Humphreys in a statement. “We don’t think cannabis is killing people, but we don’t think it’s saving people.”

In this latest study, Stanford researchers employed the same method used in 2014, evaluating the connection between legalized medical marijuana and fatal opioid overdoses. Though they confirmed the findings of that study, the results changed when they examined opioid deaths up until 2017. By that point, 47 American states had legalized medical and/or recreational marijuana in some fashion, compared to just 13 states through 2010.

Ultimately, they found that states with legal medical marijuana had a higher rate of death from opioid overdoses.

When comparing states where the drug was legal to those still illegal, Humphreys and his team found no correlation between opioid overdose mortality and the level of marijuana use restriction.

“There are valid reasons to pursue medical cannabis policies, but this doesn’t seem to be one of them,” adds postdoctoral scholar and lead author Chelsea Shover. “I urge researchers and policymakers to focus on other ways to reduce mortality due to opioid overdoses.”

The study was published in the Proceedings of the National Academy of Sciences.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

Our Editorial Process

StudyFinds publishes digestible, agenda-free, transparent research summaries that are intended to inform the reader as well as stir civil, educated debate. We do not agree nor disagree with any of the studies we post, rather, we encourage our readers to debate the veracity of the findings themselves. All articles published on StudyFinds are vetted by our editors prior to publication and include links back to the source or corresponding journal article, if possible.

Our Editorial Team

Steve Fink


Chris Melore


Sophia Naughton

Associate Editor