The prevalence of psychotic symptoms among methamphetamine users

Aims To examine the prevalence of psychotic symptoms among regular methamphetamine users. Design Cross-sectional survey. Setting Participants were recruited from Sydney, Australia, through advertisements in free-press magazines, flyers and through word-of-mouth. Participants Methamphetamine users (n = 309) who were aged 16 years or over and took the drug at least monthly during the past year. Measurements A structured face-to-face interview was used to assess drug use, demographics and symptoms of psychosis in the past year. Measures of psychosis included: (a) a psychosis screening instrument derived from the Composite International Diagnostic Interview; and (b) the Brief Psychiatric Rating Scale subscales of suspiciousness, unusual thought content, and hallucinations. Dependence on methamphetamine was measured using the Severity of Dependence Scale. Findings Thirteen per cent of participants screened positive for psychosis, and 23% had experienced a clinically significant symptom of suspiciousness, unusual thought content or hallucinations in the past year. Dependent methamphetamine users were three times more likely to have experienced psychotic symptoms than their non-dependent counterparts, even after adjusting for history of schizophrenia and other psychotic disorders. Conclusion The prevalence of psychosis among the current sample of methamphetamine users was 11 times higher than among the general population in Australia. Dependent methamphetamine users are a particularly high-risk group for psychosis.