Medicine: marijuana linked to psychosis?

Sounds like something right out of Reefer Madness.

He and his colleagues studied 2,437 young people aged 14-24 and identified those with a predisposition for psychosis. They also questioned them about their cannabis use and followed them up for four years.

For those of you not in the medical field and not used to examining experimental design, this is called a prospective study, not a randomized control trial, which is the essential tool for producing medical knowledge. A prospective study is not an experiment at all, is inherently riddled with confounding factors, and while often information can be gleaned from these studies, they're more like decent leads than they are evidence of anything unto themselves.

“The results show that in the group without vulnerability to psychosis, there was a small effect of cannabis on the onset of psychotic symptoms four years later,” Van Os said.

“But this risk was four times bigger in individuals who had a personal vulnerability to psychosis.”

Van Os said the study also showed the odds of experiencing symptoms of psychosis were higher for people who smoked cannabis more frequently.

So, people who are predisposed to psychosis who smoke more marijuana experience more psychosis? Maybe their marijuana useage is linked to their predisposition for psychosis (as if psychosis were one disorder, and not a zillion different ones of different etiologies) instead? Point being, studies like this should only preach to the choir. They're interesting, and somewhat suggestive. But they can easily be a load of shit just as well.

And this from someone's who has never smoked a joint in his life!