Stranger homicide by people with schizophrenia is rare -- and unpredictable

International study led by Sydney researchers shows homicides of strangers by people with schizophrenia are exceptionally rare and unpredictable events

A study initiated by a team of Sydney researchers published today (Monday 12 October) in the leading schizophrenia journal, Schizophrenia Bulletin, shows that homicides of strangers by people diagnosed with schizophrenia are exceptionally rare events.

The study is one of a series of studies of homicide by the mentally ill by two senior lecturers in psychiatry at the University of New South Wales, Dr Olav Nielssen at St Vincents Hospital and Dr Matthew Large at Prince of Wales. This study is an international collaboration with researchers in Canada, Finland and the Netherlands. An international multicentre study was necessary as there were so few stranger homicides by people with mental illness in NSW in the last 15 years.

The study calculated a rate of stranger homicide by those with schizophrenia of one in 14 million population per year in advanced countries. It also compared the characteristics of 42 patients who killed strangers with a matched sample of patients who killed family members. The stranger homicide offenders were more likely to be the homeless and to have a history of antisocial conduct. The victims were more likely to be males and the offences rarely occurred in the victim's home or workplace. More than half of the subjects in both groups had never received treatment for schizophrenia.

"The lack of any particular distinguishing features and the extremely low base rate means that it would be impossible to predict who might commit this sort of offence and when they might occur" said Dr Nielssen. "However, most of the patients in the study were not receiving treatment, and providing earlier treatment to first episode patients, and a good standard of care to all patients with established illness could prevent some of these tragic events".

"What the paper shows, more than anything else, is that the public fear of the mentally ill is completely misplaced" said Dr Large. "These events are so rare that they are almost impossible to study, yet the fear of serious violence by the mentally ill is a major cause of stigma".

October 11, 2009