Opioid Deaths Not Reduced by Medical Marijuana


The investigators believe that medical marijuana provides benefits and that research into its effectiveness should continue.

A new study through the Stanford University School of Medicine has found that legalizing medical marijuana does not reduce the rate of fatal opioid overdoses. The study published inProceedings of the National Academy of Sciencesfound no evidence of a connection between opioid deaths and the availability of medical cannabis.

Its findings contradict a 2014 study, which found that there were lower rates of fatal opioid over-doses in states that had legalized marijuana for medical purposes than in states where marijuana remained legal.

For the study, investigators used a similar method to a 2014 study in order to evaluate the connection between legalized medical marijuana and fatal opioid overdoses. Investigators originally confirmed the findings of the 2014 study; however, when they viewed the opioid deaths leading up to 2017, where many states had legalized some form of medical marijuana, they found that it contradicted it. States with legal medical marijuana had a higher rate of deaths due to opioid overdose.

According to the authors, the results of the 2014 study may have reflected policies and conditions in states that legalized medical marijuana early. Often, they note, those states tended to be wealthier and more politically liberal, with greater access to addiction treatment and naloxone.

“The states that legalized pot early also incarcerate fewer people for drug use,” said Keith Humphreys, PhD, senior author. “When people are released from prison, where they lack access to drugs and lose tolerance to them, they may try to use the same levels as they did before they were incarcerated, leading to overdose.

Currently, 47 states permit some version of medical marijuana.

Chelsea Shover, PhD, the lead author of the study, believes that medical marijuana provides benefits and that research into its effectiveness should continue.

"There are valid reasons to pursue medical cannabis policies, but this doesn't seem to be one of them," Shover said. "I urge researchers and policymakers to focus on other ways to reduce mortality due to opioid overdoses."


  1. Association between medical cannabis laws and opioid overdose mortality has reversed over time. Proceedings for the National Academy of Sciences of the United States of America website. Published June 10, 2019.https://www.pnas.org/content/early/2019/06/04/1903434116. Accessed June 11, 2019.

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