Objective: The aim of this study is to evaluate the associations between
alcohol-cannabis use and forensic/stressful events with the risk of
incident clinical psychosis during follow-up.
Method: A community-based sample (n: 2142) was screened for
clinical psychosis (schizophrenia and other psychotic disorders,
affective disorders with psychotic features) at baseline and follow-up.
Thus, incident clinical psychosis cases to develop during follow-up
(individuals with no clinical psychosis at the baseline assessment and
with clinical psychosis at the follow-up assessment) were detected (n:
27). These cases and the controls who did not report any psychotic
symptoms at the follow-up assessment (n: 1691) were compared for
exposure to environmental risk factors during follow-up (total n: 1718).
Results: Individuals reporting heavy alcohol drinking or cannabis
use during follow-up had significantly higher risk of incident clinical
psychosis. The monthly frequency of drinking and cannabis use was
also associated with the risk. Higher number of stressful life events
exposed predicted higher risk of incident clinical psychosis. The risk of
incident clinical psychosis was significantly higher in case of coexistence
of two risk factors (heavy drinking, cannabis use, ≥3 stressful events),
in comparison with the existence of a single risk factor (17.7 vs. 1.6%,
Conclusion: Heavy drinking, cannabis use, forensic events and stressful
events were associated with the risk of incident clinical psychosis. The
coexistence of multiple stressful events and disorders related to abuse of
alcohol/cannabis should be considered as a warning for the development
of clinical psychosis.