Among people with severe mental illness, a combination of three risk factors -- having been a victim of violence during childhood, living in a neighborhood where violence is common, and having a substance abuse problem -- can increase the likelihood of violent behavior more than tenfold, the researchers found. Without any of these risk factors, those with severe mental illness were no more likely to engage in violent behaviors than people in the general population without a psychiatric disorder.
"Acts of violence by people with mental illness are rare," said Jeffrey Swanson, Ph.D., associate professor of psychiatry and behavioral sciences, a sociologist at Duke and lead author of the study. "While the illness certainly plays a role, the risk factors we examined compound the illness in a way that makes violence more probable. Those risk factors should be a large part of the focus of treatment and services for persons with mental illness and a history of violence."
Swanson noted, "violent crimes committed by psychiatric patients become big headlines and reinforce the social stigma and rejection felt by many individuals who suffer from mental illness. But our findings suggest that serious violence is the rare exception among all people with psychiatric disorders. The public perception that people who are mentally ill are typically violent is unfounded."
The study appears in the September 2002 issue of the American Journal of Public Health and was funded by the National Institute of Mental Health (NIMH).
The researchers conducted confidential interviews with 802 adults from North Carolina, New Hampshire, Maryland and Connecticut who had been treated for severe psychiatric conditions such as schizophrenia, bipolar disorder or major depression.
Participants in this observational study were asked whether they had committed any acts of violence toward others during the previous year that involved the use of weapons or caused physical injury to another person. Overall, the prevalence of violence was 13 percent. Among participants who did not have any of the three risk factors cited above, less than 2 percent reported acting violently. Those who had a combination of two of the risk factors had nearly a 10 percent likelihood of violent behavior during a one-year period. Adding a third risk factor tripled the likelihood of violent behavior to about 30 percent.
"The prevalence and pattern of violent behavior found in this study supports previous research findings on the link between violence and mental illness," said Swanson. "A great deal of the violence in our mentally-ill participants appears to be attributable to factors outside of their illness. Those acts of violence are quite uncommon overall, and there are typically a number of other factors involved, like living in an impoverished high-crime neighborhood. However, when violence does occur, it requires that a disproportionate amount of public resources be spent on treatment in institutional settings -- which are the most restrictive and also the most expensive."
Swanson said many of the tragedies caused by violent behavior of people with mental illness are preventable with the appropriate resources. Yet many individuals with serious and disabling psychiatric disorders are not receiving the treatment and support that might enable them to live productive lives in the community, especially as states restrict their services in response to budget pressures.
"If we're worried about violence among people with serious mental illness, we need to pay far more attention to finding safe housing in decent neighborhoods, mitigating the effects of physical and sexual victimization, and aggressively treating substance-abuse issues," said Marvin Swartz, M.D., professor of psychiatry at Duke and an author on the study.
According to the NIMH, about one in five Americans suffers from some form of mental illness, and even the most severe forms of mental illness such as schizophrenia, bipolar disorder and major depression are highly treatable with medication and therapy. Commonly used medications include atypical antipsychotics and selective serotonin reuptake inhibitors, newer classes of drugs that have fewer side effects than older alternatives.
According to a 1999 Surgeon General's report, the indirect costs of all mental illness imposed a nearly $79 billion loss on the U.S. economy in 1990, the most recent year for which such estimates are available. Most of that amount reflects loss of productivity because of illness, premature death, incarceration and lost work time of individuals providing care to a family member or loved one with mental illness.
Other authors on the study include H. Ryan Wagner, Ph.D. and Keith Meador, M.D. of Duke University Medical Center; Susan Essock, Ph.D. of Mount Sinai School of Medicine and the Veterans Affairs New York Healthcare System; Fred Osher, M.D. of the University of Maryland School of Medicine, Baltimore; Lisa Goodman, Ph.D. of Boston College and the University of Maryland, College Park; and Stanley Rosenberg, Ph.D. of Dartmouth Medical School.