BACKGROUND Reports suggest a high prevalence of substance misuse in psychotic disorders but few studies examine comorbidity at onset of psychosis.
AIMS To identify the prevalence and pattern of substance use and misuse in first-episode psychosis, and relationships with diagnosis, mode of presentation and demographic variables.
METHOD Consensus diagnoses for 168 subjects presenting with first-episode psychosis were made using ICD-10 diagnostic criteria. Information on substance use and misuse was obtained from multiple sources. We examined associations between substance misuse, diagnosis and demographic factors.
RESULTS Criteria for drug use, drug misuse or alcohol misuse were met by 37% of the sample. One-year prevalence rates were 19.5% (drug misuse) and 11.7% (alcohol misuse). Thirteen subjects (8.4%) received a primary diagnosis of substance-related psychotic disorder; a significant increase compared with an earlier cohort from the same catchment area. Drug misuse was associated with younger age of onset of psychosis, male gender and non-African-Caribbean ethnicity.
CONCLUSIONS This study confirms high rates of substance misuse at onset of psychosis. There is evidence for an increase in diagnosis of substance-related psychotic disorders over time. Those most at risk of substance misuse are young males.