Drugs increase risk of violence more than schizophrenia
Schizophrenia and other psychotic illnesses are not responsible for any additional risk of violence above the increased risk associated with substance abuse, according to a novel meta-analysis published in the open access journal PLoS Medicine. The findings may have implications for attempts to reduce violence in society, suggesting that strategies aimed at reducing drug and alcohol abuse would be more successful than focusing on mental illness.
The opinion emerging in the last couple of decades that there is a modest association between schizophrenia and violence is thought to have influenced policy and legal developments, with the number of patients in secure hospitals increasing in Western countries. Many mental health charities and clinicians specializing in mental health contest this opinion - arguing that the perception that people with mental illness are more violent is a myth reinforced by the media, contributing to a social stigma around mental illness that damages many people and prevents understanding.
Researchers from Karolinska Institutet and Oxford University have now conducted a systematic review – a so called meta-analysis – of all previous studies examining psychotic illness and the risk of violence to try and resolve their varied conclusions. Using statistical tools to allow for the differences between the studies, the researchers found that the risk of violent outcomes did increase with individuals with schizophrenia or other psychoses.
However, when analysing the characteristics that differed between the studies, including study location and whether the diagnosis was for schizophrenia or another psychotic disorder, the researchers found that substance abuse was the only factor causing variation between the studies. Substance abuse greatly increased the risk of violence of those with a psychotic illness, but this increased risk of violence was similar to those in the general population with substance abuse but no psychotic illness - suggesting that most of the excess risk of violence in psychotic patients appears to be mediated by the abuse of drugs and alcohol.
The authors acknowledge that further research is needed to clarify the relationship between schizophrenia and other psychoses, substance abuse, medication adherence and violence. However, the authors suggest that their findings could help redress the stigmatization of patients with schizophrenia and other psychoses. They conclude: "As substance use disorders are three to four times more common than the psychoses, public health strategies to reduce violence could focus on the prevention and treatment of substance abuse at an individual, community and societal level."
Schizophrenia and violence: systematic review and meta-analysis.
PLoS Med. 2009 Aug;6(8):e1000120