Objective: The purpose was to determine the prevalence of substance use and its impact on outcome 3 years after presentation for a first-episode of psychosis.
Method: Subjects were 203 consecutive admissions to an early psychosis program. Assessments included substance use, positive, negative and depressive symptoms and social functioning. Assessments occurred at baseline, and 1-, 2- and 3-year follow-ups.
Results: The prevalence of substance misuse was high with 51% having a substance use disorder (SUD), 33% with cannabis SUD and 35% with an alcohol SUD. Numbers with an alcohol SUD declined considerably by 1 year and for cannabis SUD by 2 years. Substance misuse was significantly associated with male gender, young age and age of onset and cannabis misuse with increased positive symptoms.
Conclusion: This study confirms the high rates of substance misuse, in particular cannabis, in first-episode psychosis. It further demonstrates that these rates can be reduced.