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Medical Marijuana Does Not, In Fact, Reduce Opioid Deaths, According to Study

Stanford’s follow-up to a 2014 UPenn study shows no such correlation.

A PPM Brief

Challenging a 2014 University of Pennsylvania (UPenn) study1 suggesting that states that legalized medical marijuana saw fewer opioid deaths (on average 25% fewer a year), researchers from the Stanford University School of Medicine recently found2 no connection between marijuana availability and opioid overdose deaths.

Using the same methods as the UPenn study, Stanford researchers sought to find an updated connection between legalized medical marijuana and fatal opioid overdoses. In the 2014 UPenn study, a time-series analysis was conducted of medical cannabis laws and state-level death certificate data in the US from 1999 to 2010, in which all 50 states were included. While the Stanford study confirmed many of the same findings from the 2014 UPenn study, researchers looked at opioid deaths up to the year 2017 (in which 29 states had legalized some form of medical or recreational marijuana; only 13 states had legalized medicinal marijuana when the UPenn study was conducted). The Stanford team found a 22.7% increase (compared to UPenn’s 25% decrease finding) in opioid-related deaths in states where medical marijuana was legal.

Legalizing medical marijuana does not necessarily curb opioid overdose deaths. (Source: 123RF)

The 2014 UPenn study results were interpreted by many medical marijuana proponents and public officials to mean that more access to medical marijuana would cause patients to turn to cannabis rather than opioids for pain relief, and if fewer opioids are used, perhaps there would be fewer overdoses. Comparing states that had more restrictive medical marijuana laws with those that allow recreational marijuana, Stanford researchers found no correlation between opioid overdose mortality and the restrictions applied in these states.

“We find it unlikely that medical cannabis — used by about 2.5% of the US population — has exerted large conflicting effects on opioid overdose mortality,” Stanford authors wrote.

In an accompanying release from Stanford Medicine,3 lead author Keith Humphreys, PhD, professor of psychiatry and behavioral sciences at its University School of Medicine, said the results of the 2014 UPenn study may have reflected policies and conditions in liberal, more wealthier states that legalized medical marijuana early, and had better access to addiction medicine and naloxone. He added that these states also incarcerated fewer people for drug use, suggesting that a former inmate being released from jail might lose their tolerance and therefore have a lower risk of overdose from opioids.

As of April 2019, medical cannabis is legal in 34 states. Learn more about medical marijuana terminology and legality here.

Last updated on: May 21, 2020
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