Coming across a Psychology Today article on “The Link Between Cannabis and Psychosis” is a little like watching this clip from The Onion. It’s a well written article but someone in a different mental state might read it as “everyone knows you’re high and it’ll probably make you go insane.” I have taken enough econometrics to suspect that there might be some selection effects in the observational studies that this article mentions. I’ve also taken enough econometrics to wonder whether I could answer this question for myself. This post chronicles my attempt to do just that.