What do we know about the effects of marijuana legalization?

Illustration by Slug Signorino

Cecil replies:

I’d say the market for studies on marijuana legalization is currently about as hot as the market for, say, late-night gas-station taquitos in the greater Denver area: i.e., torrid. Much as the public craves results, though, the fact remains that legalized recreational weed is just a few years old in the handful of states that allow it. Data’s coming in steadily, but it’s preliminary, and therefore wide open to interpretation.

Your traffic-accident query is a good example of how far into the weeds one can get here. Take Colorado, where recreational marijuana has been legal the longest — since 2012, officially, though business really started booming in 2014 with the advent of licensed retail outlets. According to analysis by the Denver Post, the number of drivers there who died in car crashes with THC in their systems more than doubled between 2013 and 2016.

OK, that doesn’t sound great. But in context it’s not so clear. For one, crash fatalities in Colorado (and in Washington, another legalization state) over roughly this period have remained in line with stats from control states where marijuana remains outlawed, per 2017 research in the American Journal of Public Health. And multiple earlier studies had previously found reduced traffic fatalities following the passage of state medical-marijuana laws.

And two, the relationship between THC and impairment remains poorly understood, even down to establishing intoxication — as anyone who’s nervously awaited a drug test will tell you, THC metabolites linger in the bloodstream long after the high has worn off. (Chugging grapefruit juice doesn’t mask those metabolites, by the way, if anyone’s still claiming it does.) We’ve had decades to observe how alcohol degrades one’s skills behind the wheel; far less time to assess the intersection of driving and weed use.

For the moment, though, what we’ve got is data to confirm anyone’s preexisting prejudices. Opposed to recreational marijuana? Legalization’s made the roads deadlier. In favor? Plenty of evidence suggests that’s not really happening. This was a provisional conclusion offered in a 2016 report by the Drug Policy Alliance, which found “stable” traffic-fatality numbers in pot-friendly states, and also that no, legalization doesn’t seem to be contributing to any increase in kids getting high.

The tax angle is more straightforward: legal pot equals big bucks. As of last year, Colorado had taken in $500 million in weed taxes, with half going to K-12 education. Municipalities can impose their own levies, too, which is how Pueblo County ended up spending $420,000 (heh heh) on scholarships for 210 local students in 2017.

Another place legal weed appears to be leaving its footprint: the opioid crisis. An AJPH study from last fall found that in the first two years of recreational marijuana being legal in Colorado, opioid-related deaths declined 6.5 percent, reversing an upward trend going back more than a decade. On the one hand, these are (once again) preliminary numbers, but on the other they track with what we know about places where medical marijuana had already been legalized — a 2014 paper calculated a 25 percent reduction in opioid-related fatalities in states with medical marijuana laws on the books compared to those without.

Meanwhile, in a survey of 224 patients in Michigan from 2016, respondents reported a 64 percent reduction in opioid use associated with their medical-pot habit, plus “decreased number and side effects of medications, and an improved quality of life.” What all this seems to be telling us is that, where possible, pain sufferers are substituting weed for opioids, and doing better for it. Switching to another reliable painkiller that poses neither a massive addiction problem nor an OD risk — who’d have thunk, right?

Predictably, this reasoning hasn’t found a home at today’s Department of Justice, where Attorney General Jeff Sessions has adopted an unmistakably weed-hostile stance overall — in January he revoked Obama-era directives telling the feds to quit prosecuting pot offenses in states that have legalized it — and specifically scoffed at the theory that marijuana’s painkilling properties could help on the opioid front. Last winter he waved off the very idea as “almost a desperate attempt to defend the harmlessness of marijuana,” adding, “Maybe science will prove I’m wrong.” Again, early studies appear to be doing so, not that Sessions is likely to care.

A first-draft scorecard, then, for legalized weed: promising on opioids, good for state budgets, and TBD on some other issues, including traffic deaths. In other words, plenty of research left for public-policy types in pursuit of the straight dope. Such as: At two Colorado animal hospitals, cases of marijuana poisoning in dogs went up fourfold after medical pot became legal, with edibles playing a role in at least a pair of fatalities. To win the war against leaving gummies on the coffee table, we’ll surely need more data than that.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.