People with mental illness are much more likely to be victims of murder than other people, a new study finds.
For the study, which was published online, researchers looked at data from the entire adult population - more than 7 million people - in Sweden between 2001 and 2008.
During that time, there were 615 murders. Of those, 22% were among people with mental-health disorders, which were grouped into five categories: substance-use disorder; schizophrenia; mood disorders, including bipolar disorder and depression; anxiety disorders; and personality disorders.
What the study found
After adjusting for other risk factors, the researchers concluded that people with mental-health disorders had a fivefold overall increased risk of death by murder.
People with substance-use disorders had the highest increased risk (about nine times higher), followed by those with personality disorders (about three times higher), depression (2.6 times higher), anxiety disorders (2.2 times higher), and schizophrenia (1.8 times higher), according to a journal news release.
One explanation for the findings is that people with mental illness are more likely to live in poor neighbourhoods, which have higher murder rates, said Casey Crump, a clinical assistant professor in the department of medicine at Stanford University, and colleagues.
People with mental-health disorders may also be in closer contact with other mentally ill people and be less aware of their safety risks.
The study authors said this type of research may help lead to more effective ways to improve the health and safety of people with mental illness. This "should include collaborations between mental-health clinics and the criminal justice system to develop personal safety and conflict-management skills among people with mental illness," they wrote.
Improved housing, financial stability and treatment for substance abuse may also lower the risk of violent crime for people with mental illness, they suggested.
The findings show that doctors need to assess the full range of potential harm faced by people with mental illness, Roger Webb and colleagues at the University of Manchester, in England, wrote in an accompanying editorial.
This would include being a victim or perpetrator of violence, abuse and bullying; suicidal behaviour; accidental drug overdoses; and other dangers associated with intoxication or impulsivity. Patients and their families should receive advice about how to avoid these threats.
Although the study found an association between having a mental illness and higher risk of being a murder victim, it did not establish a cause-and-effect relationship.
The National Alliance on Mental Illness has more about mental