Systematic review of the international literature on the epidemiology of mentally disordered offenders

NHS Centre for Reviews and Dissemination
Record ID 31999009325
Authors' objectives:

This report covers studies of mentally disordered offenders (MDOs) in the General Population, in Special Hospitals, in the Criminal Justice System and in the General Psychiatric Services System. A review is also included of the literature on mental disorder and homicide.

Authors' recommendations: General population studies: The prevalence of mentally disordered offenders up to the age 26-30 is between 2.1 and 2.8 per hundred for men and about half this for women. All types of mental disorder seem to be associated with all types of crime, but particularly violent crime. Conduct problems in childhood seem to be good predictors of future mentally disordered offenders. Secure psychiatric service population: There are about 100 patients in special hospitals per 3 million population, and there are four times as many men as women. The average age is in the 30's but there is a wide age range. About two thirds of patients are legally classified as mentally ill and a quarter as having a personality disorder. The number of patients with mental impairment is small and growing smaller. The average length of stay is 8 years with a rather longer length of stay for women. About two thirds of patients have an index offence of violence against the person, and for about a quarter of all patients this has involved homicide. Non-white groups are over-represented in the Special Hospitals, making up almost 20% of the population. It is estimated that at least half the patients in special hospitals do not require the highest level of security; the number needing high security provision is estimated to be less than 50 per 3 million of the general population, though there is regional variation. Many patients do require long-term treatment and care in conditions of medium or low security, but achieving this is not easy. About a third of those discharged to less secure provision are returned to special hospitals. General psychiatric services population It is clear from the studies reviewed that the prevalence of mentally disordered offenders in the general psychiatric population is small. Generally speaking, people who have been diagnosed with schizophrenia or learning disabilities are not dangerous to others, nor do they commit criminal offences at a greater rate than the general population. However, it is also clear that there are small numbers of people with either one or other diagnosis who do present a danger to others, both in hospital and in the community, and who need specialist provision. Studies of homicide: The major findings of the studies reviewed are that homicide offenders tend to be young men, are often schizophrenic, alcohol/drug abusers and/or have antisocial personality disorder. There is, however, no all-inclusive recipe to identify either a homicide offender or a mentally disordered homicide offender. Several, but by no means all, will have been seen by criminal justice and/or psychiatric services before. Even specific types of homicides do not appear to have particular distinguishing characteristics. Male homicide offenders seem to be about ten times as likely to commit future homicides compare to other men. The criminal justice system population About 2% of the sentenced prisoner population have a psychosis, though the rate of schizophrenia is somewhat higher than in the general populationoutside prison. However, about 40% of men and over 50% of women sentenced prisoners have some form of identifiable mental disorder. Self-reporting methods of diagnosis are highly unreliable, but do confirm the large extent of present or past mental disorder amongst the prison population. About 25% of sentenced men in prison, and over 40% of sentenced women, have been estimated by qualified psychiatrist researchers, using clinical criteria, to require psychiatric treatment or further assessment; only about one third of these are currently receiving treatment, and for some this treatment is inappropriate. About 3% of the sentenced prisoner population require transfer to psychiatric hospital. A third of these are not currently receiving any treatment. About 60% would need secure hospital provision.
Authors' methods: Systematic review
Project Status: Completed
Year Published: 1999
English language abstract: An English language summary is available
Publication Type: Not Assigned
Country: England
MeSH Terms
  • Commitment of Mentally Ill
  • Forensic Psychiatry
  • Mental Disorders
  • Mental Health Services
  • Schizophrenia
Organisation Name: University of York
Contact Address: University of York, York, Y01 5DD, United Kingdom. Tel: +44 1904 321040, Fax: +44 1904 321041,
Contact Name:
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Copyright: Centre for Reviews and Dissemination
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