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

Objective: 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.

Methods: 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.

Results: 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).

Conclusions: 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.