Trying to replicate an often-cited 2014 study that found that states with medical marijuana laws had lower opioid overdose death rates, Stanford University researchers looked at deaths over a longer period of time. Their conclusion: States with such laws have actually seen an increase in opioid overdoses.
The new study looked at states that legalized medical marijuana between 1999 and 2017, instead of 1999 and 2010, as the original John Hopkins University study did. In the seven years after 2010, 32 more states enacted medical marijuana laws, and opioid overdose deaths skyrocketed around the country.
The Stanford study confirmed the Hopkins study's findings. States who enacted a medical marijuana law between 1999 and 2010 saw about a 25% drop in opioid overdose deaths per 100,000 residents.
But when the Stanford researchers expanded their data to 2017, they found that states with medical marijuana laws eventually saw a 22.7% increase in opioid overdose deaths.
This doesn't mean that medical marijuana laws are driving higher opioid overdose rates, the researchers cautioned. It's just an indication that medical marijuana and opioid overdoses may not be all that closely linked.
"(It's wrong) to say cannabis was saving lives before, and it's killing people now. I don't think that makes sense," Chelsea Shover, the lead author of the study, said Tuesday. "It's more to say, hey, when two things aren't causally related, it's not surprising that the relationship will change over time. Both cannabis legalization and strategies to deal with the opioid crisis are extremely important issues. What we're saying is, talk about them separately."
Still, many states have begun to turn to medical marijuana as a possible tool in the fight against a devastating opioid crisis. Last year, Pennsylvania became the first state in the country to approve medical marijuana to treat opioid use disorder, and tapped eight universities around the state to begin conducting research into its medical applications.
Rachel Levine, Pennsylvania's secretary of health, said Tuesday that she hadn't yet read the new study. "We never thought we were going to fix the opioid crisis with medical marijuana," she said of the state's approval. "The idea is to provide one more tool in the toolbox."
Some patients have said cannabis helps to curb the anxiety and cravings that can plague early opioid recovery: "It puts you in a place that's a lot more balanced," medical marijuana patient Briana Kline told The Philadelphia Inquirer last summer. She was using marijuana along with Suboxone, an opioid-based drug that's considered one of the gold standards for addiction treatment. "It's a lot easier to get through the day and not think about things that you shouldn't."
But there is far more research on the efficacy of opioid-based medication-assisted treatments than there is on whether marijuana helps with recovery.