[Crimes committed by mentally ill persons in the years 1977-1999. Development, number and causes].

INTRODUCTION: In line with many other countries, Denmark has reorganised psychiatric care with closure of 50% of the psychiatric beds in favour of community mental health. Parallel to this reorganisation the number of forensic patients has increased.

MATERIAL AND METHODS: In Denmark, the majority of forensic patients are under supervision by a probation officer. As from 1977, The Department of Prison and Probation has registered the monthly prevalence of forensic patients, from 1989 also the monthly incidence and decrease. These data have been used to analyse the trends in the number of forensic patients.

RESULTS: The number of forensic patients increased from 297 in 1980 to 1134 in 1999, the increase in prevalence being exponential with an annual growth rate of 6.79%. The incidence figures showed an exponential increase with an annual growth rate of 5.96% (95% confidence interval 4.76%-7.27%). The annual growth rate for the decrease is 6.18%. Thus, the three growth rates do not differ, meaning that the increasing number of forensic patients is the result of an increasing intake.

DISCUSSION: The growing number of mentally ill offenders cannot be explained by changes of the Danish penal law concerning mentally abnormal offenders nor by changes in administrative or diagnostic practice. The number of reported crimes in Denmark has remained unchanged from 1987. The main reason for the exponential growth rate is an increasing number of schizophrenic patients committing crimes. It is concluded that deinstitutionalisation is the main reason for this development.