Another Study Finds No Evidence That Medical Marijuana Increases Cannabis Consumption by Teenagers

A
few weeks ago, in a column about the impact of marijuana
legalization, I
noted that there is not much evidence to support the frequently
voiced
fear that allowing medical use encourages teenagers to smoke
pot. A new study by three economists reinforces that
point, finding that the adoption of medical marijuana laws is not
associated with increases in cannabis consumption by high school
students. “Our results are not consistent with the hypothesis
that legalization leads to increased use of marijuana by
teenagers,” write D. Mark Anderson of Montana State University,
Benjamin Hansen of the University of Oregon, and Daniel Rees of the
University Colorado in a working paper
published by the National Bureau of Economic Research.

Anderson et al. used data from three sources:
the National Youth Risk Behavior Survey, the National
Longitudinal Survey of Youth, and the Treatment Episode Data Set.
“These analyses provide further evidence that
youth marijuana consumption does not increase with
the legalization of medical marijuana,” they write.
“Our results are not consistent with the hypothesis
that the legalization of medical marijuana caused an increase
in the use of marijuana among high school students. In
fact, estimates from our preferred specification are small,
consistently negative, and are never statistically
distinguishable from zero.”

The impact of general legalization, of course, might be
different. Assuming that legal marijuana businesses in places such
as Colorado and Washington eventually displace the black market,
teenagers will find it harder to buy pot directly, since licensed
sellers, unlike your average street dealer,
check IDs to make sure buyers are at least 21. But it may
become easier for teenagers to obtain pot indirectly, via legal
buyers. Still, Anderson et al.’s findings are significant, because
in some states (including Colorado, Washington, and California) the
rules for obtaining medical marijuana are loose enough that it’s
easy for recreational consumers to pose as patients. In fact,
critics commonly complain that medical marijuana in those states is
legalization by another name. Rees nevertheless
told The Washington Post that the overall
results of this study hold true for individual states as
well. “No single state stood out,” he said. “The
effect of passing a medical marijuana law on youth consumption
appears to be zero across the board.”