Well, at my high school, the "stoners" were also drinking, sniffing glue, eating nutmeg, smoking banana peels, etc. In adult life, the few people I've met who only smoke weed have been pretty level-headed. There's some selection bias because I try to avoid people who appear to be of the glue-sniffing variety. Maybe they're just big reefer junkies after all.
I wouldn't call adults who casually smoke weed stoners though. We're talking about people who are long-term or chain smokers. High school pot smokers do not yet show the long-term signs of marijuana use typically.
