Criminal and violent behavior in schizophrenic patients: an overview.

An overview of the most important older and newer results regarding the relationship between violent and criminal behavior on the one hand and schizophrenic illness on the other hand is presented. Four different methods are available to study this relationship: (i) study of the prevalence of mental illness in criminal/violent populations; (ii) study of criminality/violence rate in samples of psychiatric patients; (iii) study of criminality/violence in community samples comparing mental patients with non-patient community residents; and (iv) study of criminality/violence in birth cohorts prospectively. All these methods have been used; but samples composed of schizophrenic patients exclusively were only exceptionally studied. The results indicate that there is a modest but significant relationship between schizophrenia and violence and crime which persists even after controlling for demographic and socio-economic variables. The probability of schizophrenic patients to be criminal or violent depends on the acuity of their illness and is increased by their use of psychoactive substances. Generally, however, violent and criminal acts directly attributable to mental illness account only for a very small proportion of such acts in the society.