Co-occurring mental illness and substance use disorder among Australian prisoners

Estimate the prevalence of co-occurring substance use disorder and mental illness in a sample of Australian prisoners, and describe patterns of co-occurring substance use disorder and mental illness.

The sample comprised 1478 individuals (1208 men, 270 women) from two surveys of prisoners' mental health: the 2001 New South Wales Inmate Health Survey, and a consecutive sample of prison receptions. Individuals were drawn from all of the state's 29 prisons. Mental health and substance use disorders were assessed using the Composite International Diagnostic Interview.

The overall prevalence of any mental disorder was 42.7% and the prevalence of any substance use disorder was 55.3%. With the exception of alcohol use disorder, women had higher rates than men of mental illness and substance use disorders. The prevalence of a co-occurring mental illness and substance use disorder in the past 12 months was 29% (46% among women vs. 25% among men). The association between cannabis use disorder and psychosis was significant for men only [odds ratio (OR)=2.4]. Among women there was a significant association between affective disorder and co-occurring alcohol use disorder (OR=2.4), and stimulant use disorder (OR=2.4).

The results highlight the high prevalence of co-occurring substance use and mental illness among prisoners. These results indicate that mental health services in prisons need to be adequately resourced to address co-occurring mental health and substance use problems, and these services need to be appropriately structured to effectively screen, manage and treat this group.