February 4, 2009

Mental illness does not up violence risk

[Posted: Tue 03/02/2009 by Deborah Condon]

People with a mental health illness are no more likely than anyone else to commit acts of violence, the results of a new study indicate.

However mental illness combined with substance abuse does increase the risk of future violence.

According to US researchers, these findings show that a link between mental illness and violence does exist, ‘but it is not as strong as some people think’.

"These findings challenge the perception some people have, and which you often see reflected in media coverage, that mental illness alone makes someone more dangerous. Our study shows that this perception is just not correct," said the study’s co-author, Dr Sally Johnson of the University of North Carolina.

The researchers carried out a statistical analysis of data collected as part of a study involving over 34,000 people.

The results showed that ‘if a person has severe mental illness without substance abuse and history of violence, he or she has the same chances of being violent during the next three years as any other person in the general population’.

The team found that when mental illness is combined with substance abuse, the risk for future violence reaches a level of statistical significance. However, even mental illness combined with substance abuse ranks only ninth on the study's list of the top 10 predictors of future violence.

The higher ranking predictors, listed in order of their predictive value, are age (younger people are more likely to commit acts of violence), history of violence, sex (males are more prone to violence), history of juvenile detention, divorce or separation in the past year, history of physical abuse, parental criminal history and unemployment for the past year. Victimisation in the past year was the tenth predictor.

"The data shows it is simplistic as well as inaccurate to say the cause of violence among mentally ill individuals is the mental illness itself…We found that several other factors are much more predictive of future violence than mental illness alone and only when a person has both mental illness and substance abuse at the same time does that person's risk of future violence outweigh anyone else's," the researchers said.

Details of these findings are published in the journal, Archives of General Psychiatry.