The prevalence of self-reported mental illness among those imprisoned in New South Wales across three health surveys, from 2001 to 2015

Objective: The prevalence of mental illness among those in prison is much higher than in the community; however, very few studies have examined whether rates have changed over time, in line with increasing self-reported rates in the community. Methods: This study compares the prevalence of self-reported mental illness, self-harm and suicidal thoughts/behaviours, and drug and alcohol use across three waves (2001, 2009 and 2015) of health surveys involving men and women in New South Wales prisons and compared these rates with published community-level findings. Results: The prevalence of those reporting any mental health diagnosis increased significantly across the three surveys, even after adjustment for socio-demographic and criminal justice variables that also changed over time. Individuals surveyed in 2015 were more likely to report a mental health diagnosis than those surveyed in 2001 (adjusted odds ratio = 2.66, 95% confidence interval = [2.16, 3.27]). The prevalence of self-harm and suicidal thoughts and behaviours remained stable across the three surveys, while self-reported regular drug use decreased over the period. Women experienced a far greater burden of mental illness than men across all three surveys and experienced more growth in the prevalence of most psychiatric disorders. Conclusion: These findings have important implications for public and prison health systems given the poor social, health and criminal justice outcomes of those imprisoned with mental illness, both in custody and post-release.