Mentally disordered offenders

Mentally disordered offenders PDF Version (10KB)

Research summary
Vol. 3 No. 3
May 1998


How dangerous are mentally disordered offenders?


Canadians are understandably concerned about threats to their personal safety, and offenders with a mental disorder are often viewed as particularly dangerous. The actual extent of this risk was addressed in an analysis of the violent recidivism of mentally disordered offenders.


A meta-analytic review of the offender literature was conducted. Meta-analysis is a quantitative technique for summarizing the results from many studies. The review consisted of 64 studies of the recidivism of mentally disordered offenders. These studies involved over 15,000 mentally disordered offenders who were released from prisons and special hospitals and subsequently followed into the community for an average of 4.8 years. In addition, all of the studies examined factors that increase the risk of violent recidivism among mentally disordered offenders.


When compared to offenders who do not have major psychological or psychiatric disorders, mentally disordered offenders are less likely to recidivate violently. There are two explanations for the lower violent recidivism rate. First, some studies compare mentally disordered offenders to individuals who have neither a mental disorder nor a criminal record. With this comparison, those with a mental disorder are more likely to be violent. However, when the comparison group consists of criminal offenders without a mental disorder, it is the criminal offender group that is more likely to act violently. Second, mentally disordered offenders are not always actively psychotic. They may be in remission or their symptoms are being managed by medication. There is some evidence to suggest that the risk for violence increases when the individual is psychotic and suffering from symptoms of a paranoid nature.

The study also evaluated the relative importance of different risk factors. Many mental health professionals place considerable emphasis on "clinical" variables. Examples are length of hospitalization and type of mental disorder (e.g., schizophrenia, manic-depression). The meta-analysis found that these variables demonstrate very weak associations with violent re-offending. Much more potent predictors of violent recidivism are the factors typically found to predict violence among non-disordered offenders. Examples of these risk factors are criminal history, unemployment and family problems.

Policy implications

  1. Police, judges and correctional staff may need to modify their perceptions of the dangerousness of mentally disordered offenders and their responses to these individuals. Compared to non-disordered offenders, the mentally disordered offender poses a lower risk to re-offend violently. Concern for community safety may be raised in situations where the offender is psychotic with paranoid symptoms.
  2. The similarities in the risk factors for mentally disordered and non-disordered offenders suggests a point where the health and criminal justice systems could integrate their approaches for effectively managing the mentally disordered offender.
  3. There are two specific areas where the two systems can cooperate: a) the area of risk assessment and, b) offender rehabilitation. The significant overlap in risk factors for the mentally disordered and non-disordered offenders indicate that the development of risk scales for the mentally disordered offender should build upon risk assessment technologies developed for general offenders. In addition, treatment programs that are intended to reduce the recidivism of the mentally disordered offender may benefit by targeting the same criminogenic factors that are the focus of successful offender rehabilitation programs rather than traditional clinical factors.


For further information

James Bonta, Ph.D.
Solicitor General Canada
340 Laurier Avenue West
Ottawa, Ontario
K1A 0P8
Tel (613) 991-2831
Fax (613) 990-8295

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