I grew up in a super poor neighborhood, and I knew maybe 10-15 kids who started smoking MJ before age 16. The only ones who had any kind of extreme cognitive fa

I grew up in a super poor neighborhood, and I knew maybe 10-15 kids who started smoking MJ before age 16. The only ones who had any kind of extreme cognitive fallout were the ones that dabbled in more extreme stuff (like PCP). Even in those cases though, it's hard to point at the drug as opposed to the reason they were using. (In the PCP case it was three brother with a mentally ill single mother) I'm not discounting the possibility that MJ can cause such things, but even the studies put the risk fairly low, and it's hard to separate environmental and genetic risks in the population they have available to study.