Researchers in Australia recently contributed new data to the body of work on the association between schizophrenia, substance abuse, and violent criminal behavior. In an article published online June 3 in Acta Psychiatrica Scandinavica, the group—including members from the Victoria Police Crime Department, the Centre for Forensic Behavioural Science at Monash University, the Victorian Institute of Forensic Mental Health, and the Institute of Psychiatry in London—examined the relationship between committing homicide, the presence of schizophrenia, and past criminality. To do so, they evaluated contacts recorded in two statewide databases, one of which recorded public mental health service contacts and the second of which recorded contacts with the police.

James Ogloff, J.D., Ph.D., a professor of clinical forensic psychology at Monash University, director of psychological services for the Victorian Institute of Forensic Mental Health, and a coauthor of the report, told Psychiatric News why the research focused on one form of violent crime: "Homicide is a unique crime not only because of its severity, but also because it has among the highest of clearance rates; that is, most crimes are solved and most offenders are identified."

Estimated rates of schizophrenia disorders, substance abuse, and criminal convictions found among the 435 homicide offenders evaluated were compared with estimated rates in two composite comparison samples. Thirty-eight of the 435 offenders (8.7 percent) had been diagnosed with a schizophrenia spectrum disorder. Rates of known substance abuse between homicide offenders with and without schizophrenia and community-dwelling residents with schizophrenia did not differ significantly. However, these rates were higher than those found in the general community. A similar pattern emerged for comparisons of offending histories between these same groups. Substance misuse was determined by reviewing the two databases used for police convictions for alcohol- or drug-related charges, and for diagnoses of substance abuse or dependence disorders.

"Patients with schizophrenia are significantly more likely than those in the general community to commit homicide offenses," said Ogloff and colleagues in the report. "Known substance abuse or prior offending rates for those with schizophrenia are not more significant indicators for risk of future offending among homicide offenders than for other groups." And "most of the women and about half of the men with schizophrenia were being treated at the time of the crime," Ogloff told Psychiatric News.

The outcomes of the study are no doubt discouraging to the mental health community's efforts to convince the public that people with mental illness are not necessarily violent individuals. But the association also can't be ignored.

Paul Appelbaum, M.D., the Dollard Professor of Psychiatry, Medicine, and Law, director of the Division of Law, Ethics, and Psychiatry at Columbia University, and a former APA president, reviewed the study for Psychiatric News. "This paper is one of a number of recent studies that have suggested that people suffering from psychotic disorders have an increased risk of violence, especially severe violence such as homicide. Indeed, taking the research as a whole—and despite studies to the contrary—one would have to say that the weight of the evidence supports that conclusion. These researchers found that, although a history of substance abuse clearly increased the rate of homicide, it did not account for it entirely."

Appelbaum added, "There is a genuine concern that these data may heighten the stigma associated with psychotic disorders. But most people with schizophrenia are not violent, and only a very small fraction of violence in the U.S. is attributable to mental illness. Overall, however, the growing body of data suggesting a link between serious mental illness and violence should motivate us to rebuild our systems for delivering care to this population."

"We have been working with the police to enhance their capabilities of dealing with mentally ill offenders, and we have been working with mental health services to assist them in understanding the factors related to a risk of violence and how they might manage patients with schizophrenia at risk for violence," Ogloff told Psychiatric News. "It was very telling in our study that the vast majority of women and about half of the men with schizophrenia had been diagnosed long before they committed homicide. Several were under the care of a mental health service at the time or shortly before they committed homicide. In a few cases, there was even a clear indication that a serious act of violence was likely. Our work shows definitively that even when factors such as substance abuse are considered, the rate of schizophrenia among homicide offenders is rather dramatically higher than we see in the general community."

The results presented in this study form part of lead author Debra Bennett's doctoral studies, which were supported by Monash University.

An abstract of "Schizophrenia Disorders, Substance Abuse, and Prior Offending in a Sequential Series of 435 Homicides" is posted at <www.ncbi.nlm.nih.gov/pubmed/21644942>.