The relationship between mental disorders and different types of crime

Previous studies of relationships between mental disorder and crime have tended to group the mental disorders, the crimes or both, leaving uncertainty about a more specific mental disorder: crime relationships.

To examine the relationship between types of mental disorder and types of crime in pre-trial defendants.

Data were extracted from 21,424 pre-trial forensic psychiatric reports made between 2000 and 2006 in the Netherlands. We compared the prevalence of axis I disorders, personality disorders, intellectual functioning and substance abuse in defendants charged with a range of crimes (homicide, attempted/threatened homicide, assault, battery, rape, sexual crimes, arson and/or property crimes) using chi-square tests. Relationships with diminished accountability, reflecting a direct relationship with underlying mental disorder, were calculated using multivariate regression models, adjusted for age, gender, ethnicity and history of judicial contact.

Arson had the strongest relationship with mental disorders in our sample, then assaults, then homicidal attempts or threats. Sexual and property crimes had the weakest relationship with diminished or absent accountability. Diminished accountability had the strongest relationship with psychotic disorders, followed by organic psychosyndromes and developmental disorders, whereas other axis I disorders, personality disorders or an IQ score of <85 points were only moderately related. These relationships varied little according to the type of crime, although tended to be weaker for defendants in property crimes. Cannabis and hard drugs were significantly associated with decreased accountability only in respect of arson.

Mental disorders are related to all types of crimes but especially to arson, battery and homicidal attempts or threats, with a court finding of diminished accountability providing some validation for perceived links between the disorder and crime in this study.

Psychiatric assessment is likely to be the most useful for defendants under charges of arson, assault or attempted homicide, as these groups are most likely to suffer from a psychiatric disorder related to the alleged offence. Psychotic, organic and some developmental disorders appear to have the strongest relationship with diminished accountability. Findings with respect to illicit drug use are likely to have more varied implications between jurisdictions but, in the Netherlands, may sometimes be accepted as diminishing accountability in defendants of arson.