“One of the most persistent controversies vis-à-vis cannabis use pertains to its effect on the risk of psychiatric disorders, particularly psychotic disorders and full-blown schizophrenia. Longitudinal investigations show a consistent association between adolescent cannabis
use and psychosis. Cannabis use is considered a preventable risk factor for psychosis.”
“Moreover, persistent cannabis use after a first episode is associated with poorer prognosis even after controlling for other substance use.”