Comorbid Mental Disorders: Prevalence and Impact on Institutional Outcomes

Research Highlights

Comorbid personality or substance abuse disorders underlie negative outcomes for offenders with a mental disorder

Why we did this study

Understanding the outcomes of offenders with various types of mental disorders is key to ensuring effective correctional supervision and intervention strategies for this notable proportion of the offender population. Previous research has indicated poorer outcomes for offenders with mental disorders but which types of disorders contributed to this was not established. The current research provided a more detailed examination of outcomes for specific disorders and combinations of comorbid disorders.

What we did

The results of the Correctional Service of Canada’s (CSC) national mental health survey (N =1,110) were used to determine prevalence rates of comorbid disorders among incoming federal male offenders, and to examine the outcomes associated with patterns of comorbidity during the offenders’ incarceration. Incoming male offenders were assessed on clinical interviews using the SCID allowing for DSM diagnoses. Outcomes of interest were: institutional misconducts, transfers to segregation and treatment centres, history of self-injury or suicidal behaviour, and participation in correctional programs.

What we found

Over 67% of offenders with a mental disorder met the criteria for at least one other mental disorder. For example, male offenders with personality disorders (PDs) comprise 48% of the incoming population and 66% of these men have a co-occurring substance use disorder (SUD). Similarly, over 50% of the incoming population had a SUD, and of these, 68% also met criteria for a co-occurring personality disorder.

Problematic behaviour while incarcerated such as involvement in misconducts and violent incidents, and placements in segregation were most prevalent among offenders comorbid with a personality disorder. Offenders with an Axis I disorder only (i.e., all mental disorders except personality disorders and mental retardation) were no more likely to be involved in misconducts or violent incidents, or to be transferred to segregation than offenders with no diagnosed disorder. This suggests that it is the symptoms of impulsivity and aggression associated with personality disorders that drive the negative outcomes for offenders with mental disorders.

Factors that explained placements in treatment centres were scores on the impairment scale of the DSM (Global Assessment of Function (GAF)) and involvement in institutional incidents. Offenders with GAF scores below 45 (serious to severe impairment) were most likely to experience a transfer to a treatment centre. Among the diagnoses associated with the greatest degree of impairment were BPD and psychotic disorders and offenders comorbid for Axis I disorders in combination with substance and personality disorders. Men with mood disorders, especially major depression and panic disorders had higher rates of suicidal and self-injury behaviour.

What it means

The outcomes for offenders with a mental disorder cannot be fully understood without consideration of the high rates of comorbidity for personality and substance abuse disorders in a correctional population and their adverse impact.

For more information

Stewart, LA, & Wilton G (2017). Comorbid mental disorders: Prevalence and impact on institutional outcomes. (R-379). Ottawa, Ontario: Correctional Service of Canada.

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