Thursday, July 27, 2017

Marijuana is bad for your grades

Economists Olivier Marie and Ulf Zölitz took advantage of a decision by Maastricht, a city in the Netherlands, to change the rules for “cannabis cafes,” which legally sell recreational marijuana. Because Maastricht is very close to the border of multiple European countries (Belgium, France and Germany), drug tourism was posing difficulties for the city. Hoping to address this, the city barred noncitizens of the Netherlands from buying from the cafes.

This policy change created an intriguing natural experiment at Maastricht University, because students there from neighboring countries suddenly were unable to access legal pot, while students from the Netherlands continued.

The research on more than 4,000 students, published in the Review of Economic Studies, found that those who lost access to legal marijuana showed substantial improvement in their grades. Specifically, those banned from cannabis cafes had a more than 5 percent increase in their odds of passing their courses. Low performing students benefited even more, which the researchers noted is particularly important because these students are at high-risk of dropping out. The researchers attribute their results to the students who were denied legal access to marijuana being less likely to use it and to suffer cognitive impairments (e.g., in concentration and memory) as a result.

Other studies have tried to estimate the impact of marijuana legalization by studying those U.S. states that legalized medicinal or recreational marijuana. But marijuana policy researcher Rosalie Pacula of RAND Corporation noted that the Maastricht study provide evidence that “is much better than anything done so far in the United States.”

States differ in countless ways that are hard for researchers to adjust for in their data analysis, but the Maastricht study examined similar people in the same location — some of them even side by side in the same classrooms — making it easier to isolate the effect of marijuana legalization.
--Keith Humphreys, Washington Post, on the opportunity cost of studying