Dr. Marcus Bachhuber, an internist at the University of Pennsylvania, says he first became interested in the relationship between access to medical marijuana and opioids in his own practice. Patients suffering from chronic nerve or back pain told him that sometimes pot was the only thing that eased their discomfort. Even patients who had tried prescribed painkillers and given them up sometimes agreed: Pot was the only thing that worked. “In thinking about this and talking about it with colleagues, I wondered how this might play out in states where medical marijuana is legal.”
In recent years, more and more scientists have begun to unravel the common idea that smoking pot entices a person to do other drugs. But in Bachhuber’s new study, published in JAMA Internal Medicine, suggests that we should rethink pot’s impact on other drug use entirely: An analysis of 13 states shows that areas with access to medical marijuana yield significantly lower death rates from painkillers and heroin.
Some 60% of people who do die of opioid overdoses have legitimate painkiller prescriptions written for them by their primary doctors. But when Bachhuber dug up death certificates between 1999 and 2010 in 13 states, he found that the states with medical marijuana laws on the books showed nearly a quarter decrease in opioid death rates compared to states without. He was surprised at the size of the difference.
“The unique contribution of this study is that we found a potentially unexpected benefit of medical marijuana laws,” he says. “This is the first study of its kind suggesting this link.”
But showing the link–even if it is a strong one–is still a long way from demonstrating cause and effect. Bachhuber and his colleagues are still stymied by the potential mechanism that might cause the decrease in death rates, though they do have some theories.
Consider, for example, that chronic pain patients really do use medical marijuana as a painkiller supplement or substitute; research supports the idea that cannabinoid receptors in the brain act as an alternative route to easing pain. Or, if painkiller deaths have a link to psychiatric disorders, some suggest that legalized pot might “lessen the drive to use opiates at lethal levels” in these patients. Then again, Bachhuber says that states’ education efforts on the dangers of overprescribing painkillers might also have had an impact. If these efforts occurred around the same time as the passage of medical marijuana laws, they might account for some of the difference.
Either way, the study calls for more investigation into possible positive public health impacts of legalized pot. As other research has shown, much of the conventional wisdom on the dangers of pot has arisen from bad interpretations, and much less from critical thinking.