“In clinical practice, we have seen many people with chronic pain who say that marijuana is the only thing that works for their pain, or even that they had tried prescription painkillers-such as Vicodin, Percocet, or OxyContin-but the only thing that works is marijuana,” said Marcus Bachhuber, MD, a primary care physician and clinical scholar, Philadelphia Veterans Affairs Medical Center and Robert Wood Johnson Foundation Clinical Scholars Program, Pennsylvania.
“We thought that if people were choosing to treat their pain with marijuana instead of opioids in states where this is legal, these states might see relatively lower rates of opioid painkiller overdoses,” he said.
Dr Bachhuber and colleagues looked at prescription painkiller overdose deaths from 1999 to 2010 in states that had medical marijuana laws and states that didn't, and controlled for the presence of absence of 3 other policies related to prescription painkillers, as well as the state and year.
They found that between 1999 and 2010, medical marijuana laws were associated with about a 25% lower rate of prescription painkiller overdose deaths, on average, relative to the years before the law and trends in non-law states.
Three states (California, Oregon, and Washington) had medical cannabis laws effective prior to 1999. Ten states (Alaska, Colorado, Hawaii, Maine, Michigan, Montana, Nevada, New Mexico, Rhode Island, and Vermont) enacted medical cannabis laws between 1999 and 2010. States with medical cannabis laws had a 24.8% lower mean annual opioid overdose mortality rate (95% CI, −37.5% to −9.5%; P=.003) compared with states without medical cannabis laws, according to the study. Examination of the association between medical cannabis laws and opioid analgesic overdose mortality in each year after implementation of the law showed that such laws were associated with a lower rate of overdose mortality that generally strengthened over time: year 1 (−19.9%; 95% CI, −30.6% to −7.7%; P=.002), year 2 (−25.2%; 95% CI, −40.6% to −5.9%; P=.01), year 3 (−23.6%; 95% CI, −41.1% to −1.0%; P=.04), year 4 (−20.2%; 95% CI, −33.6% to −4.0%; P=.02), year 5 (−33.7%; 95% CI, −50.9% to −10.4%; P=.008), and year 6 (−33.3%; 95% CI, −44.7% to −19.6%; P< .001). In secondary analyses, the findings remained similar.
“Medical marijuana is advocated by many as a safer alternative to opioids for treatment of chronic pain,” Dr Bachhuber said. “Based on this, managed care plans could start thinking about including it in their formularies in states where it is legal.”
The unique contribution of this study is that it provides evidence of a possible unexpected public health benefit of medical marijuana laws and policy, according to Dr Bachhuber. “Beyond providing access to medical marijuana for individuals, our findings suggest that these laws may have broader impacts on public health which should be studied.”