The association between psychosis and problematical drug use among Australian adults: findings from the National Survey of Mental Health and Well-Being

Background. The present paper aimed to: (a) provide Australian estimates of the population-level association between psychotic 'caseness' and substance use; (b) examine liability to problematical substance use according to 'caseness' via the conditional prevalence (prevalence among users); and (c) examine associations between problematical substance use and the number of psychotic symptoms using ordinal logistic regression. Method. Data were from the National Survey of Mental Health and Well-Being (NSMHWB), a stratified multi-stage probability sample of Australian adults, using a subset of persons under the age of 50 years (N = 6722). A screener assessed the presence of characteristic psychotic symptoms. Associations between 'case' status and DSM-IV alcohol, cannabis and other drug use disorders were examined. Ordinal logistic regressions predicting psychosis scores were carried out, including demographic, mental health and drug use variables. Results. Ninety-nine persons (1.2 %) screened positively for psychosis. Regular tobacco, alcohol and cannabis use were much more common among persons screening positively, as were alcohol, cannabis and other drug use disorders. Among alcohol and cannabis users, psychosis 'cases' were much more likely to be dependent. Ordinal logistic regressions revealed that regular tobacco use, cannabis and alcohol dependence, and opiate abuse were predictors of psychosis scores. Conclusions. The mental health risks of problematical substance use need to be disseminated to persons at risk of, or suffering from, psychotic illness, and to heavy substance users. Work is needed to develop effective treatment approaches for problematical substance use among persons with psychosis.