Differences in associations between cannabis and stimulant disorders in first admission psychosis

Substance use in early psychosis is associated with male gender and earlier onset. Evidence about other correlates of substance use is less consistent. Stimulants (e.g. methamphetamine, cocaine) may precipitate psychosis. However the associations of stimulant disorders in early psychosis are difficult to examine because of lower prevalence and overlap with cannabis disorders.

Hospital records were used to identify 9919 persons aged 15-29 with a first hospital admission with psychosis in New South Wales (NSW), Australia. Correlates of illicit drug disorders, cannabis disorders and stimulant disorders were examined using univariate and multivariate logistic regression.

Half of first psychosis admissions had comorbid substance diagnoses. Cannabis and stimulant disorders were increased more than ten-fold compared to the age-matched Australian population. Stimulant disorders were equally common in women and men and associated with urban location, social advantage and older age at first admission. Cannabis disorders were associated with male gender, younger age and non-metropolitan location. Diagnoses of drug-induced psychoses were more strongly associated with stimulants than with cannabis. Compared to people with cannabis diagnoses alone, those with both cannabis and stimulant disorders were older, more likely to have a diagnosis of drug-induced psychosis and more likely to have comorbid alcohol disorders.

Cannabis is the most commonly used substance in psychosis, and the associations of illicit drug use in psychoses are largely those of cannabis disorders. There are significant differences between the personal, socio-economic and diagnostic correlates of cannabis and stimulant disorders in young people with first admission psychosis.