Experts Narrow List Of Violence Risk Factors

The subject of violence and mental illness is complex and controversial. For instance, the one-year prevalence rate of violence committed by mentally ill people has been estimated to be anywhere between 7 percent and 58 percent, depending on the types of patients studied and the methodology used. And numerous risk factors for violent behavior by mentally ill people have been cited—anger, aggression, impulsiveness, mood disturbance, delusions, hallucinations, substance abuse, and so forth.

Thus, Jeffrey Swanson, Ph.D., an associate professor of psychiatry and behavioral sciences at Duke University Medical Center, Marvin Swartz, M.D., a professor of psychiatry at Duke, and colleagues undertook a study to pinpoint better the prevalence of violence among seriously mentally ill patients being treated in public mental health facilities and to pinpoint risk factors for violent behavior in this particular population.

As they reported in the September American Journal of Public Health, the one-year prevalence rate for violence in the particular group they studied was 13 percent, and three major risk factors for violence in this particular population were identified—having been a victim of violence in childhood, being currently exposed to violence, and abusing substances.

Swanson and his team recruited 802 subjects with serious mental illness from the public mental health systems of four states. They came from a state psychiatric hospital and two community mental health centers in New Hampshire, two city mental health centers in Connecticut, two community mental health centers in Maryland, a psychiatric inpatient unit of the Durham, N.C., Veterans Affairs Medical Center, and some other inpatient and outpatient units in North Carolina.

The subjects provided detailed information about any violent behavior in which they had engaged during the previous year—that is, any assault causing bodily injury or use of a lethal weapon to threaten someone. They answered detailed questions about any physical or sexual abuse they had experienced before or after age 16. They provided demographic and social-environmental information, such as age, sex, race, marital status, income, or exposure to violence in their current environment. Subjects’ psychiatric diagnoses, use of substances, functional impairment, and whether they were complying with their psychiatric medication regimens were also assessed.

The researchers analyzed the data to determine the one-year prevalence of violent behavior among the subjects. Thirteen percent of the subjects reported having committed violent acts during the previous year.

The investigators then assessed their data to determine which demographic, social, environmental, or clinical variables contributed to violent behavior. Homelessness and exposure to community violence were found to be associated with violent behavior to a statistically significant degree. So were substance abuse, self-rated mental health status as “poor,” onset of a psychiatric disorder before age 19, psychiatric admission during the past year, and having been victimized by violence.

Finally, the scientists analyzed the data to determine the relative importance of these risk factors for violence. They found that the three most important factors were past victimization by violence, exposure to violence in the current environment, and substance abuse. They also found that the one-year predicted probability of violent behavior in the population they studied was virtually nonexistent if none of these three risk factors was present; that it was about 2 percent if either substance abuse, violent victimization history, or current exposure to violence was present; that it was between 7 percent and 10 percent if two out of the three risk factors were present; and that it was 30 percent if all three risk factors were present.

Psychiatric News asked former APA President Paul J. Fink, M.D., to give an opinion about the study report since he has a special interest in the subject of violence and the mentally ill. “I think it is a terrific article,” he said. “My understanding was that the mentally ill are much more violent when they have been drinking or using drugs. But I didn’t think that abuse, especially abuse that continues through life, was so serious. That’s a new finding, I think.”

One of the practical implications of these results, the researchers concluded in their report, is that “better-focused and -targeted interventions that assess and anticipate risk of violence [in such a mentally ill population] could reap very worthwhile benefits.”

When Psychiatric News asked Swartz and Swanson for examples of such interventions, they cited programs that address trauma consequences among the seriously mentally ill and programs that treat both mental illness and substance abuse simultaneously in the seriously mentally ill.

Swartz also commented on the implications of the findings for clinical psychiatrists. “A history of trauma and ongoing substance abuse are important risk factors for violence,” he replied. “Both need to be explored in routine history taking. In addition, psychiatrists should inquire about the community environment of the patient and support efforts to find community housing that reduces the risk of exposure to high-crime and high drug-abuse environments.”

The study was funded by National Institute of Mental Health grants and a Veterans Affairs Epidemiologic Research and Information Center grant.

An abstract of the study, “The Social-Environmental Context of Violent Behavior in Persons Treated for Severe Mental Illness,” is posted on the Web at www.ajph.org/cGI/content/full/92/9/1523. ▪