Severe Mental Illness Alone Does Not Predict Violent Crime

Marlene Busko

February 04, 2009

February 4, 2009 — Contrary to popular perception, individuals with schizophrenia, bipolar disorder, or major depression alone are no more likely than others to commit violent crimes, a new study reveals.

Future violence, such as fighting, sexual assault, or arson, was statistically more likely among individuals with severe mental illness only in the presence of comorbid substance abuse and/or dependence, according to data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC).

"Factors such as young age, male sex, parental criminal history, recent divorce, and recent unemployment were stronger predictors of future violence than mental illness," study author Eric B. Elbogen, PhD, from the University of North Carolina at Chapel Hill, told Medscape Psychiatry.

However, having 3 combined factors — severe mental illness, substance abuse or dependence, and a history of violence — was linked with a nearly 10-fold greater risk of future violence than having mental illness alone.

"Clinicians could use this [finding] as a red flag to detect patients who should undergo a more formal violence risk assessment," said Dr. Elbogen.

The study is published in the February issue of the Archives of General Psychiatry.

Potentially Unwarranted Stigma

When a violent incident such as school shooting is committed, the general public's first reaction is often to think that the perpetrator must have been mentally ill, said Dr. Elbogen.

Research on the relationship between mental illness and violence has been inconclusive, however, often due to poor study design, he said. Reliable data are needed to inform public-health policy and to prevent potentially unwarranted stigmatization of mentally ill people.

To clarify the relationship between severe mental illness and violent behavior, the researchers analyzed data on mental health and violence from NESARC, a 2-wave, face-to-face survey of a national sample of civilians living in the United States.

A total of 34,653 subjects completed interviews in 2001–2003 and in 2004–2005.

At the first interview, 10.4% of subjects had schizophrenia, bipolar disorder, or major depression only, and 9.4% had co-occurring mental disorders and substance dependence.

Subjects were asked about risk factors, including age, sex, education, income, employment status, recent job loss or divorce, history of perpetrating or being a victim of violent crime, and parental criminal activity.

In the second interview, subjects were asked whether they had committed any violent crimes since the baseline interview.

Other More Important Predictors of Dangerous Offenses

Although a recent national survey showed that 75% of the population view people with mental illness as dangerous, the current study 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 3 years as any other person in the general population," the authors write.

The 8 strongest predictors of violence, in order of strength of prediction, were younger age, history of a violent act, male sex, history of juvenile detention, divorce or separation in the past year, history of physical abuse, parental criminal history, and unemployment for the past year. Co-occurring mental illness and substance use was ninth on the list, followed by victimization in the past year.

"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," the authors write.

"Instead, the current study finds that mental illness is clearly relevant to violence risk but that its causal roles are complex, indirect, and embedded in a web of other (and arguably more) important individual and situational cofactors to consider," they add.

No financial disclosure was reported.

Arch Gen Psychiatry. 2009;66:152-161. Abstract

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