Owing to the fact that Finnish police have been able to solve about 95% of all homicides during recent decades and because most homicide offenders are subjected to an intensive psychiatric evaluation, it was possible to examine data on 693 of 994 homicide offenders during an 8-year period.
The prevalences of mental disorders of the homicide offenders were used to calculate odds ratios (ORs) for the statistical increase in risk associated with specific mental disorders.
The results indicate that schizophrenia increases the OR of homicidal violence by about 8-fold in men and 6.5-fold in women. Antisocial personality disorder increases the OR over 10-fold in men and over 50-fold in women. Affective disorders, anxiety disorders, dysthymia, and mental retardation did not elevate the OR to any significant extent (OR <5.0).
Homicidal behavior in a country with a relatively low crime rate appears to have a statistical association with some specific mental disorders classified according to DSM-III-R classifications.