Students’ marks improve after change in dagga sale policy

THESE colle ge students lost access to legal dagga – and started getting better marks.

The most rigorous study yet of the effects of marijuana legalisation has identified a disturbing result: college students with access to recreational cannabis on average earn worse marks and fail classes at a higher rate.

Economists Olivier Marie and Ulf Zölitz took advantage of a decision by Maastricht, a city in the Netherlands, to change the rules for “cannabis cafés,” which legally sell recreational marijuana.

Because Maastricht is very close to the border of three European countries (Belgium, France and Germany), drug tourism was posing difficulties for the city.

Hoping to address this, the city barred non-citizens of the Netherlands from buying from the cafés.

This policy change created an intriguing natural experiment at Maastricht University, because students there from neighbouring countries suddenly were unable to get legal dagga, 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 marks.

Specifically, those banned from cannabis cafés had a more than 5% 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 highrisk of dropping out.

The researchers attribute their results to the students who were denied legal access to dagga being less likely to use it and to suffer cognitive impairments (for example in concentration and memory) as a result.

Other studies have tried to estimate the impact of marijuana legalisation by studying those US states that legalised medicinal or recreational marijuana.

But marijuana policy researcher Rosalie Pacula of RAND Corporation said the Maastricht study shows evidence that “is much better than anything done so far in the US”.

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 legalisation.

Also, Pacula pointed out that since voters in US states are the ones who approve marijuana legalisation, it creates a chicken and egg problem for researchers (that is, does legalisation make people smoke more dagga, or do dagga smokers tend to vote for legalisation?)

This methodolo gical problem was resolved in the Maastricht study because the marijuana policy change was imposed without input from those whom it affected.

Although this is the strongest study to date on how people are affected by marijuana legalisation, no research can ultimately tell us whether legalisation is a good or bad decision: That’s a political question and not a scientific one.

But what the Maastricht study does is it provides highly credible evidence that marijuana legalisation will lead to decreased academic success – perhaps particularly so for struggling students – and that is a concern that both proponents and opponents of legalisation should keep in mind.

Humphreys is a professor of psychiatry at Stanford University and is an affiliated faculty member at Stanford Law School and the Stanford Neurosciences Institute. - The Washington Post