"We would expect the adverse consequences of opioid use to decrease over time in states where medical marijuana use is legal, as individuals substitute marijuana for opioids in the treatment of severe or chronic pain," said June H. Kim, a doctoral student at the Mailman School of Public Health, and the study's lead author, in a press release.
The study, published today in the American Journal of Public Health, is the first to look at the relationship between medical marijuana laws and individual-level laboratory measurements of opioid use. The results suggest a fairly straightforward conclusion that "in states with medical marijuana laws, fewer individuals are using opioids," the authors write.
It adds to a growing body of evidence suggesting that chronic pain patients may substitute marijuana for prescription painkillers in states where the option is available.
One paper published earlier this year found that Medicare Part D prescriptions for painkillers declined significantly in states that passed medical marijuana laws. Other studies have shown that medical marijuana states see fewer painkiller overdose deaths than states without medical pot, and that access to medical marijuana dispensaries is also linked to declining rates of opiate overdose and death.
In a sign some drugmakers might be worried about marijuana's impact, the company behind the powerful painkiller fentanyl recently poured half a million dollars into the campaign opposing full marijuana legalization in Arizona, one of the biggest-ever single donations to an anti-legalization cause.
The DEA is also moving to increase restrictions on another natural drug, kratom, that some opiate addicts say they have used to kick their painkiller habit.
More from Wonkblog: