Study Examines Association Between Mental Illness and Violent Behavior


Violence appears to be more common among those with mental illness only when they also report substance abuse or dependence, according to a report in the February issue of Archives of General Psychiatry, one of the JAMA/Archives journals.


Researchers have been studying the connection between mental illness and violent behavior for the past 20 years, but there is controversy regarding how to interpret the links, according to background information in the article. “The relationship between mental illness and violence has a significant effect on mental health practice and policy, guides allocation of the limited resources in the mental health and criminal justice systems and serves as the basis for imposing mandatory treatment to protect public safety at the expense of patients’ self-determination and liberty,” the authors write. “Reliable data are needed to properly inform public perception about the relationship between mental illness and dangerousness to avoid potentially unwarranted stigmatization of people with mental illness.”


Eric B. Elbogen, Ph.D., and Sally C. Johnson, M.D., of the University of North Carolina at Chapel Hill School of Medicine assessed data collected as part of the National Epidemiological Survey on Alcohol and Related Conditions, a survey conducted by the National Institute on Alcohol Abuse and Alcoholism. A total of 34,653 individuals were interviewed about their mental health, demographics, history of violence and other risk factors between 2001 and 2003. The participants then answered questions about any violent behavior—including fighting, sexual assault and starting fires—perpetrated between then and a second interview (conducted between 2004 and 2005).


At the first interview, 10.87 percent of participants were diagnosed with schizophrenia, bipolar disorder or major depression alone, 21.41 percent with substance abuse or dependence alone and 9.4 percent with a severe mental disorder plus substance abuse or dependence.


Having a mental illness alone at the first interview did not predict whether an individual would have violent behavior before the second interview. However, individuals with both mental illness and substance abuse or dependence were at higher risk for future violence. “The highest risk was shown for dual-disordered subjects with a history of violence, who showed nearly 10 times higher risk of violence compared with subjects with severe mental illness only,” the authors write.


Other factors that predicted future violence included a history of juvenile detention, physical abuse or having witnessed parental fighting; a recent divorce, unemployment or victimization; or being younger, male or lower-income. Most of these risk factors were present more often in individuals with mental illness.


“Because severe mental illness did not independently predict future violent behavior, these findings challenge perceptions that mental illness is a leading cause of violence in the general population,” the authors conclude. “Still, people with mental illness did report violence more often, largely because they showed other factors associated with violence. Consequently, understanding the link between violent acts and mental disorder requires consideration of its association with other variables such as substance abuse, environmental stressors and history of violence.”


Arch Gen Psychiatry. 2009;66[2]:152-161