Cannabis use is associated with an increased risk of developing psychotic disorders among people already at clinical high risk for psychosis. In a prospective study of this population, cannabis use was linked to a higher incidence of psychotic disorders and to more persistent psychotic symptoms, as well as poorer functional outcomes. The findings strengthen evidence that cannabis acts as a risk factor for psychosis, though the direction of causality remains debated.
From 2006 to 2016, the incidence rate of cannabis-induced psychosis in Denmark rose from 2.8 to 6.1 per 100,000 person years. A corresponding increase occurred in dual diagnoses of schizophrenia with cannabis use disorder, while alcohol-induced psychosis decreased. Other substance-induced psychoses showed no clear trend. The rise in cannabis-induced psychosis parallels increases in both cannabis use and the THC content of cannabis, and changes in diagnostic practice do not appear to account for the increase.