Mental illness has always provided a convenient if frequently erroneous explanation for acts of aggression and violence. Although evidence is somewhat mixed, the vast body of data points to the mentally ill as being more likely to be the victims of violence rather than the perpetrators.
Recent research by professor Eric Elbogen, PhD, published in the Archives of General Psychiatry, confirms that mental illness alone does not increase the risk of violence. However, if combined with other risk factors such as substance abuse, the risk increases.
Youth and a history of violence were the top two predictors of violence, followed by male gender and a history of juvenile detention. Other predictors of violence included severe mental illness couple with substance abuse, a history of physical abuse, parental criminal past and being the victim of a crime in the past 12 months.
The study used data from the National Epidemiologic Survey on Alcohol and Related Conditions. Over 43,000 interviews were conducted during 2001-2002. Three years later, over 34,000 were re-interviewed.
During the first set of interviews, around 11 percent of the sample reported a diagnosis of either schizophrenia, bipolar disorder or major depression. Over 21 percent had substance abuse issues and just under 10 percent reported a severe mental illness combined with a substance abuse problem. These figures reflect the proportions found in the general population.
During the second set of interviews, Elbogen asked questions about sexual assault, fighting, setting fires and other acts of violence. In the case of schizophrenia, just over five percent of the sample reported some form of violent behavior. When coupled with substance abuse or dependence, nearly 13 percent reported violent behavior. In the case of those with a combined mental illness and substance abuse problem the rate of violence was ten times higher than those with mental illness only.
Elbogen refers to one survey of attitudes to mental illness in which 75 percent of respondents considered people with mental illness as dangerous. "Our study shows that a link between mental illness and violence does exist, but it's not as strong as most people think," said Elbogen. "Several other factors are much more predictive of future violence than mental illness alone," he stated.