Mental Disorder, Intellectual Deficiency, and Crime

• Studies of criminality among patients in psychiatric hospitals and of mental disorder among incarcerated offenders have suggested an association between the major mental disorders (schizophrenia and major affective disorders) and crime. However, these investigations are characterized by notable methodological weaknesses, and, consequently, this conclusion has remained tentative. Little is known about the criminality of intellectually handicapped people. The present study examined the relationship between crime and mental disorder and crime and intellectual deficiency in an unselected Swedish birth cohort followed up to age 30 years. It was found that men with major mental disorders were 21/2 times more likely than men with no disorder or handicap to be registered for a criminal offense and four times more likely to be registered for a violent offense. Women with major disorders were five times more likely than women with no disorder or handicap to be registered for an offense and 27 times more likely to be registered for a violent offense. These subjects committed many serious offenses throughout their lives. The criminal behavior in over half these cases appeared before the age of 18 years. Intellectually handicapped men were three times more likely to offend than men with no disorder or handicap and five times more likely to commit a violent offense. Intellectually handicapped women were almost four times more likely to offend than women with no disorder or handicap and 25 times more likely to commit a violent offense. The results of this investigation confirm and extend previous findings indicating that individuals with major mental disorders and those with intellectual handicaps are at increased risk for offending and for violent offending. However, in the United States, where rates of crime overall and crime by substance abusers are very high, the mentally disordered and intellectually handicapped would account for only a small proportion of these offenses.