The authors, researchers from Oregon State University and the University of Michigan, note that this could be because teens who drink heavily might be more open to other forms of substance use—either because they are bigger risk-takers, or less religious, or for some other reason. (The authors looked at both smoking pot and eating cannabis-laced edibles.)
In spite of this study, it’s still not clear whether recreational marijuana legalization leads to a mass uptick in getting high. Teens overall have grown more accepting of marijuana in recent years, and this study found that pot use was on the rise in colleges in almost all the states. Past studies have found that following legalization, marijuana use went up among 8th and 10th graders in Washington state, but not in Colorado, or among high-school seniors in either state.
Interestingly, though, this study does suggest that legal marijuana, at least among college kids, does not seem to have much of a substitution effect. Contrary to the predictions of some legalization enthusiasts, teens don’t seem to be foregoing binge drinking—arguably a more physically harmful practice—in order to smoke weed. Instead, they’re doing both.
We still need more studies to know if that will be the case for adults, or for college students in other states. In some ways, it’s good news that legalization didn’t seem to induce students who are otherwise drug-averse to start smoking pot in large numbers. But this paper does poke a hole in one popular health-based argument for legalizing marijuana: that doing so will make it replace alcohol.