Protracted marijuana use (which many of my students don't consider to be using drugs) often results in what I think of as the shards of a broken mirror--here and there you see flashes of the brilliance that used to be, but the individual can no longer put it together to make a complete image.
It is sad. The New York Times is calling for legalization of marijuana:
Repeal Prohibition, Again. I don't have a strong opinion about it...
When I was in school, I also knew a couple kids who had apparent brain damage from smoking too much pot. One of them was a (formerly) bright guy. The kids used to talk about it: "So-and-so smokes too much pot, and look what he's done to himself." TBH, I think those kids taught the rest of us a lesson because what they had done to themselves was just
so obvious.
This is another one of those stories showing that gifted kids in high SES environments are susceptible to things like irrational thinking and/or making incredibly bad life-changing mistakes.
I see it as much the same as ethanol in most ways. Legalization would address other problems, though (the kind that come from trafficking in anything illegal).