States with medical marijuana see greater rise in illicit and problem use, study finds

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Sorry to harsh everybody's buzz, but we've got some bad news: Over the past few decades, states with medical marijuana laws have seen a bigger bump in illicit and cannabis use disorders than states without a weed program.

That's the conclusion drawn from research out of Columbia University's Mailman School of Public Health and Columbia University Medical Center, which published their findings in JAMA Psychiatry. The authors analyzed U.S. national survey data collected in 1991-1992, 2001-2002 and 2012-2013 from 118,497 adult participants to track these trends.

Overall, rates of illicit and problem marijuana use have risen nationally since 1991 — a year that predates any medicinal pot program in the country — but that uptick was "significantly" steeper in states that have made steps toward legalization. Prohibition states saw a rise in the prevalence of illegal marijuana use from 4.5% of adults in 1991 and 1992 to 6.70% in 2012 and 2013, while the rate in states with medical marijuana jumped from 5.55% to 9.15%. Likewise, where cannabis disorders increased from 1.35% in 1991-1992 to 2.30% in 2012-2013 for states without legal weed, they went from 1.48% to 3.10% in states that regulate and tax marijuana.

This study cuts against the grain of other, mostly positive reports about the consequences of legal marijuana. In Washington and Colorado, for example — two states that allow the sale of recreational weed in addition to medicinal cannabis — marijuana arrests plummeted, suggesting that stats on "illicit" use are more a function of prohibition laws that voters have often rejected at the ballot box. What's more, neither Washington nor Colorado has experienced a swell in teenage marijuana use. Marijuana use among Colorado teens, in fact, has declined by around 12% year-over-year since legalization.  

Medical marijuanaSource: Robert F. Bukaty/AP
Medical marijuana  Robert F. Bukaty/AP

Deborah Hasin, lead author of the Columbia study, agreed that teens appear to have gone largely unaffected by shifting marijuana policy. That's why her team turned their focus to an older demographic. "The laws may not be too relevant and salient to teenagers so we thought it was important to look at adults," Hasin told Reuters Health

Hasin's research on this topic hasn't been without controversy. In 2015, she and others published a study that showed a national spike in cannabis disorders, but a follow-up paper led by Richard A. Grucza of Washington University School of Medicine undermined those numbers, producing data in which no such increase was observed. Grucza criticized Hasin's methodology, too, noting that "individuals underreport socially proscribed behaviors in face-to-face interviews" of the type Hasin relied on, whereas he had the more reliable results of private computer survey results. That underreporting makes all the difference, he said, "because only those who report past-year use are assessed for marijuana use disorder" — and as the social stigma of marijuana fades in the legalization era, participants are of course more likely to discuss their marijuana use than in previous years, creating a false sense that more and more people are using  — and becoming addicted — to pot.      

Hasin's new study was funded in part by the National Institute on Drug Abuse, which cites Hasin's own previously challenged estimate that "30% of those who use marijuana may develop some degree of marijuana use disorder" — yet they also report a 9% addiction rate, which also raises some questions about how problematic use is defined in the first place. Mason Tvert of the pro-weed Marijuana Policy Project said that if Hasin's criteria were applied to drinking culture, then 80% of Americans would be considered alcoholics.   

"This particular researcher has spent the last few years trying to link marijuana policy reform to an increase in marijuana use disorders," Tvert said. "Her studies rely on questionable data that appears to be the only data available to support her hypothesis, and she ignores all the evidence that contradicts it."

Even so, there are strong indications that American attitudes toward marijuana are relaxing, with usage climbing as a result. That surge may partly be, as Grucza argues, the effect of people coming out of the closet about their relationship with the drug — and Hasin's research doesn't establish a causal link between legalization and illicit or problem cannabis use. But to the extent that one can develop a weed addiction in any degree (another matter for debate), Hasin's main takeaway seems inarguable: "If you increase the prevalence of users," she said, "you are going to increase the prevalence of people who have adverse consequences."

And if that's not enough to spoil your high, you must be smoking the good stuff.