Five years ago, a team of researchers rifling through death certificate data uncovered an unexpected trend: Opioid-related deaths were a whopping 25 percent lower in the 13 states that had legalized medical marijuana, compared to those that hadn’t.
There was nothing in the study that demonstrated a causal link between the two statistics, and the authors cautioned against overinterpreting the findings. Regardless, advocates for legal cannabis quickly began to leverage the study as evidence that medical marijuana, which could offer an alternative to prescription painkillers for patients with chronic pain, could become the next big thing in the fight against the opioid epidemic.
Now, new research published today in the journal PNAS suggests the story is far more complicated, Olga Khazan reports for The Atlantic. The study, which used methods identical to its 2014 predecessor, also found that, between 1999 and 2010, opioid-related deaths declined in states that had introduced medical marijuana. But in the years following, the trend began to reverse—and by 2017, the overall picture was looking bleak: Over the past two decades, states with cannabis-related legislation have actually seen a 23 percent increase in deaths from opioid overdoses.
“If you think opening a bunch of dispensaries is going to reduce opioid deaths, you'll be disappointed,” study author Keith Humphreys, a psychiatrist and behavioral scientist at Stanford University, said in a statement. “We don't think cannabis is killing people, but we don't think it's saving people.”
Since California legalized medical marijuana in 1996, 46 additional states have passed legislation permitting some version of cannabis in clinical settings. But in the same timespan, the United States’ opioid epidemic has ballooned, with close to 50,000 Americans dying from opioid overdoses each year.
That certainly doesn’t imply that marijuana use is enabling opioid use. But the new study’s sobering finds do indicate that cannabis legislation probably won’t provide the panacea many hoped for.
In the study, state death statistics didn’t show a lasting dip in opioid-related deaths after the passage of medical marijuana laws. These findings didn’t change when the researchers considered the differences between states that allowed recreational cannabis use—thus giving its residents more access to marijuana—and those with more restrictive laws.
It’s still not clear why the two studies yielded such different results. One possible explanation, however, could be cultural. The 13 states in the 2014 study were, on average, wealthier and more politically liberal, Humpheys said in the statement. In these regions, patients also had more access to treatments for addiction and naloxone, which can prevent overdose fatalities. Geographically, these 13 states also fell mostly in the American West, where the opioid epidemic arrived later, study author Chelsea Shover told Khazan at The Atlantic.
The trajectories of marijuana and opioids may not be as entangled as once thought. Chinazo Cunningham, a physician at the Albert Einstein College of Medicine and author of the original study, told Khazan that she agrees that marijuana should not be considered a “silver bullet” for the opioid epidemic. But, she adds, cannabis can still play a role in pain management in general.
More work is needed to figure out how—or even if—marijuana’s palliative effects can be put to good use in avoiding addictive painkillers. Either way, cannabis legislation alone won’t be enough to solve the opioid epidemic.
“I wish it were true. I wish that passing medical cannabis [laws] would solve the opioid crisis,” Shover told Lenny Bernstein at The Washington Post. “But the evidence doesn’t support that.”