Proportion of crimes attributable to mental disorders in the Netherlands population.

The proportion of crimes attributable to mental disorders in the population (population attributable risk, PAR) is estimated to be 5.2% for violent crimes and 15.7% for arson [1] . However, only a minority of crimes committed by mentally ill defendants is directly attributable to the underlying mental disorder [2] . The relationship between crime and mental disorders is confounded by socioeconomic status, previous institutionalization, coexisting substance abuse, and personality disorders [3] . We had the unique opportunity to examine the PAR for crime fully attributable to mental illness, as accountability for indicted crimes is routinely assessed in pre-trial reported defendants in the Netherlands [4] . A severe psychiatric disorder, usually of psychotic nature, is a necessary condition for a finding of “not accountable” and absolves a person of guilt. The total number of crimes and defendants between 2000 and 2006 was obtained from the national Dutch registry. The PAR of crimes fully attributable to mental disorders was calculated as the fraction of persons deemed “not accountable” out of the total number of defendants.