Mentally Ill at Significant Risk of Becoming Murder Victims

Caroline Cassels

March 05, 2013

Individuals with mental illness are at significantly increased risk of being murdered, new research shows.

A nationwide cohort study in Sweden showed that those with any mental disorder had a 5-fold increased risk of dying by homicide compared with their counterparts without mental illness.

"In this large cohort study, people with mental disorders had highly increased risks of homicidal death, irrespective of sex, age, or other sociodemographic characteristics. Although the risk of homicidal death was highest among those with substance use disorders, it was also increased among those with personality disorders, depression, anxiety disorders, or schizophrenia and did not seem to be explained by comorbid substance use," the investigators, led by Casey Crump, MD, PhD, Stanford University in California, write.

The study was published online March 5 in BMJ.

Although much attention has been paid to the perpetration of homicide by the mentally ill, the researchers note that very little notice has been paid to this population's risk of being homicide victims.

"People with mental disorders may be at increased risk of homicidal death for several reasons, including a high prevalence of comorbid substance use, which is associated with violence. Irrespective of substance use, they are also more likely to live in high deprivation areas, which have higher homicide rates, be in closer contact with other mentally ill people, be less aware of their safety needs, or potentially be victimized because of perceptions that they are dangerous or vulnerable," the authors write.

The investigators assessed mental disorders and homicides across the entire population of Swedish adults from 2001 to 2008, a total of some 7.2 million people.

During 54.4 million person-years of follow-up, there were a total of 615 homicidal deaths (410 men and 205 women). These included 141 homicidal deaths (104 men and 37 women) of persons with mental illness. Crude mortality rates with regard to deaths due to homicide (per 100,000 person-years) were 1.1 in the entire population and 2.8 among those with mental illness vs 0.9 among those without mental illness.

Adjusted analyses revealed that any mental disorder was associated with a 4.9-fold (95% confidence interval [CI], 4.0 - 6.0) risk for homicidal death compared with people without mental illness.

The researchers also report that although the risk of death by homicide was highest among those with substance use disorders (hazard ratio [HR], 9.37; 95% CI, 7.39 - 11.88), the risk was also significantly increased among those with schizophrenia (HR, 1.82; 95% CI, 0.85 - 3.86), anxiety disorders (HR, 2.16; 95% CI, 1.32 - 3.52), depression (HR, 2.55; 95% CI, 1.70 - 3.83), or personality disorders (HR, 3.21; 95% CI, 1.70 - 6.06).

The investigators note that the risk factors for homicidal death were similar to those linked to suicide and accidental death in this patient population.

They further suggest that interventions such as improved collaboration between mental health clinics and the criminal justice system, as well as better housing, financial stability, and substance abuse treatment, would make individuals with mental illness less vulnerable to violent crime.

In an accompanying editorial, Roger Webb, PhD, senior research fellow in psychiatric epidemiology at the University of Manchester, United Kingdom, and colleagues note that the study has implications for clinical practice.

Key among them is the need for clinicians to screen for the "full array of risk factors for adverse outcomes that may befall people with mental health problems."

"This would include being a victim of violence as well as committing it, abuse and bullying, suicidal behaviour, accidental drug overdoses, and other major adverse events linked with intoxication or impulsivity."

They also note that national mental health strategies "should reflect the broad nature of safety concerns in mental healthcare, while anti-stigma campaigns among the public should aim to counter fear of mentally ill people with sympathy for the risks they face."

The authors and editorialists report no relevant financial relationships.

BMJ. Published online March 5, 2013. Full article, Editorial

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