For the libertarians around, sorry - one deflationary piece of research… "‘High’ Achievers? Cannabis Access and Academic Performance (CESifo Working Paper No. 5: http://www.iza.org/en/webcontent/publications/papers/viewAbstract?dp_id=8900) looks at "…how legal cannabis access affects student performance."
To deal with a bunch of pesky econometric issues, the study looks at data generated by "…an exceptional policy introduced in the city of Maastricht which discriminated legal access based on individuals’ nationality." So the authors used a difference-in-difference approach on a panel data set of over 54,000 course grades of local students enrolled at Maastricht University before and during the partial cannabis prohibition.
"We find that the academic performance of students who are no longer legally permitted to buy cannabis increases substantially. Grade improvements are driven by younger students, and the effects are stronger for women and low performers. In line with how THC consumption affects cognitive functioning, we find that performance gains are larger for courses that require more numerical / mathematical skills. We investigate the underlying channels using students’ course evaluations and present suggestive evidence that performance gains are driven by improved understanding of material rather than changes in students’ study effort."
Guess that explains why he wasn't any good in Topology either...