Fatal overdoses involving narcotic painkillers are about 25 percent less common in states with medical marijuana laws than in states that do not allow patients to use cannabis for symptom relief, according to a study published online today by JAMA Internal Medicine. In 2010 alone, the authors calculate, that difference translated into 1,729 fewer deaths than would otherwise have been expected.
The researchers, led by Marcus A. Bachhuber, an internist at the V.A. Medical Center in Philadelphia, looked at data for all 50 states from 1999 through 2010, a period when opioid overdose deaths nearly doubled. That upward trend was less pronounced in the 13 states that enacted medical marijuana laws during those years. Furthermore, "such laws were associated with a lower rate of overdose mortality that generally strengthened over time." On average, states saw a 20 percent reduction the first year after implementing medical marijuana laws, a difference that rose to more than 33 percent by the sixth year. "Although the exact mechanism is unclear," Bachhuber et al. conclude, "our results suggest a link between medical cannabis laws and lower opioid analgesic overdose mortality."
The authors suggest a few possible explanations:
Patients with chronic noncancer pain who would have otherwise initiated opioid analgesics may choose medical cannabis instead….In addition, patients already receiving opioid analgesics who start medical cannabis treatment may experience improved analgesia and decrease their opioid dose, thus potentially decreasing their dose-dependent risk of overdose. Finally, if medical cannabis laws lead to decreases in polypharmacy—particularly with benzodiazepines—in people taking opioid analgesics, overdose risk would be decreased.
Notably, Bachhuber et al. found that state policies aimed at preventing nonmedical use of opioids, such as prescription monitoring programs, were not associated with lower overdose rates. "If the relationship between medical cannabis laws and opioid analgesic overdose mortality is substantiated in further work," they write, "enactment of laws to allow for use of medical cannabis may be advocated as part of a comprehensive package of policies to reduce the population risk of opioid analgesics."
University of Maine psychologist Marie J. Hayes, who co-authored a commentary that accompanied the study, told Reuters that doctors generally have strong misgivings about recommending marijuana to patients. Still, she said, Bachhuder et al.'s findings could be important. "We don't put [marijuana] in Rite Aid because we're confused by it as a society," she said. Yet "everything we're doing [to reduce opioid overdoses] is having no effect, except for in the states that have implemented medical marijuana laws."
[Thanks to Paul Armentano for the tip.]