Henquet et al. [92] studied the relation between cannabis use and psychotic symptoms in individuals at risk for psychosis who first used cannabis during adolescence. They tracked 2,437 subjects (14–24 years) with and without risk for psychosis from the general population for 4 years and found a dose-dependent increased risk of psychosis in subjects exposed to cannabis [92]. Interestingly, predisposition to psychosis was not found to be a predictor of future cannabis use at 4-year follow-up. Adding to these studies, Stefanis et al. [207] reported that both positive and negative symptoms can be induced by cannabis consumption and are independent of each other.
