Comorbid Mental Disorders: Prevalence and Impact on Community Outcomes

Research Highlights: Comorbid personality or substance misuse disorders underlie higher revocation rates for offenders with mental disorders


No R-404

May 2018

Research at a glance - PDF

Comorbid Mental Disorders: Prevalence and Impact on Community Outcomes

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 significant proportion of the offender population. An earlier study completed in Correctional Service of Canada (CSC; Stewart & Wilton, 2017) found poorer institutional outcomes for offenders with mental disorders who also have comorbid diagnoses for personality (PD) or substance use disorders (SUD). Offenders with an Axis I disorder only (without SUD or PD) were no more likely to be involved in misconducts, to be instigators in assault related incidents, or to be placed in segregation than offenders with no diagnosed mental disorder. The current research analyzed the link between mental diagnosis and outcomes on conditional release.

What we did

The current research used the results of a national mental health survey that assessed incoming men offenders
(N =1,110) on the SCID (a clinical interview protocol). These results were used to determine prevalence rates of mental disorders among incoming federal men offenders. The 7 most frequent combinations of diagnoses were identified and the associated on these patterns of comorbidity with revocation of any kind and revocation with an offence was examined and compared to offenders without a disorder.

What we found

Results confirmed the findings of the previous research indicating that federally-sentenced men with mental health diagnoses (Axis 1) that are combined with concurrent diagnoses for substance use disorders and personality disorders had the poorest outcomes and the highest rates of functional impairment. Offenders with an Axis 1 disorder in the absence of comorbid disorders had similar rates of revocations as offenders with no disorders. These results were upheld when factors related to correctional outcomes were controlled.

Previous international research has produced conflicting results on the role of mental disorder as a risk factor for general criminal offending. The current study provides strong evidence that it is largely the symptoms common to personality disorders, in combination with substance misuse problems that contribute to the higher level of criminality among individuals with a mental disorder. A diagnosis in the absence of these problems does not attenuate correctional outcomes or explain violent behaviour. (An exception to this may be when the positive symptoms of a serious mental illness are active). Failure to take into account the role of comorbidity may explain the inconsistency in research related to mental disorder and criminality.

What it means

From a policy point of view these results point to the need for offenders with mental health challenges to be provided with interventions that directly target their criminogenic need factors (Andrews & Bonta, 2010) in addition to treating their serious mental health problems. Addressing the mental health problems in the absence of assessing and addressing features of impulsivity, emotional reactivity, and antisocial orientation is unlikely to improve correctional outcomes of mentally disordered offenders in the criminal justice system.

For more information

Stewart, LA, Gamwell, L., & Wilton G (2018). Comorbid mental disorders: Prevalence and impact on community outcomes. (R-404).Ottawa, Ontario: Correctional Service of Canada.

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