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Violence in schizophrenia-spectrum disorders: patterns of offending and victimisation

posted on 22.03.2017, 01:49 authored by Short, Tamsin Bernice Renfree
Schizophrenia is a rare but complex psychiatric disorder which can have adverse effects on cognition, emotion and behaviour. The relationship between schizophrenia and crime has been the subject of voluminous research over the past century, but remains the subject of clinical and academic debate. This research thesis sought to clarify the relationship between schizophrenia-spectrum disorders and criminal violence, taking into account the role of co-morbid substance use-disorders. This information is important not only for the mental health workers who treat and manage schizophrenia-spectrum patients, but also for police officers who often serve on the ‘frontline’ between the mental health and criminal justice systems. A robust case-linkage methodology was adopted, linking information contained in state-wide mental health and criminal records databases to compare patterns of criminality between schizophrenia-spectrum patients and community controls. The schizophrenia sample comprised all persons diagnosed with a schizophrenia-spectrum disorder in the Victorian public mental health system in the years 1975, 1980, 1985, 1990, 1995, 2000, and 2005. The control sample was a randomly selected group of Victorians who had never been diagnosed with a schizophrenia-spectrum disorder. This thesis comprised three related empirical studies. The first study characterised the public mental health system in the Australian state of Victoria, a jurisdiction of approximately 5.5 million citizens. The results indicated that the public mental health system is under significant demand from the community, with many people contacting services for reasons other than psychiatric illness. It was found that the majority of intensive public mental health services are accessed by patients with schizophrenia-spectrum disorders, confirming these disorders as having high treatment needs. The study also used contact with the public mental health system to approximate lifetime prevalence of schizophrenia, and found it to be remarkably consistent with national and international estimates over the past century (0.7%). This indicated that schizophrenia, although a relatively rare disorder, has some degree of temporal stability. The second empirical study compared criminal and violent offending in 4,168 schizophrenia-spectrum disorder patients with a randomly selected control sample of 4,641 individuals without schizophrenia. Schizophrenia-spectrum patients were significantly more likely than the community controls to have committed both violent and non-violent crimes, even if they did not have a known co-morbid substance-use disorder. However, the risk of violence was particularly high in those patients with co-morbid substance misuse. The schizophrenia-spectrum patients were also more likely to be involved in family violence incidents attended by police, and to have intervention orders taken out against them. The third empirical study was the first to compare official rates of crime victimisation between schizophrenia-spectrum patients and community controls. Contrary to expectations, the schizophrenia sample had a lower overall rate of crime victimisation than the community controls. However, they were significantly more likely than controls to be affected by family violence and to have a record of physical or sexual crime victimisation, highlighting the unique vulnerabilities of this population. Taken together, this research confirmed that the majority of people with schizophrenia-spectrum disorders are neither violent nor criminal. However, it also demonstrated that in comparison to the general population, people with schizophrenia-spectrum disorders are statistically more likely to experience violent crime, both as perpetrators and victims. Thus, in this era of deinstitutionalisation, people with schizophrenia-spectrum disorders should be seen as an at-risk population with unique needs and vulnerabilities. Implications of the results for police, mental health workers, patients, and the general community are considered.


Principal supervisor

Stuart D. M. Thomas

Additional supervisor 1

Jim Ogloff, Paul Mullen

Year of Award


Department, School or Centre

Psychology and Psychiatry

Campus location



Doctor of Philosophy

Degree Type



Faculty of Medicine Nursing and Health Sciences