New research is calling into question the common assumption that mental illness is often directly responsible for an individual’s criminal behavior.
The study, published in the American Psychological Association’s (APA) journal Law and Human Behavior, found that only about 7.5% of crimes committed by people with serious mental disorders were the direct result of their symptoms.
“Although offenders with mental illness are overrepresented in the criminal justice system, psychiatric symptoms relate weakly to criminal behavior at the group level,” the researchers wrote.
According to the study, roughly 15% of individuals incarcerated in the United States suffer from a serious mental illness such as schizophrenia, major depression or bipolar disorder. Previous research by the U.S. Bureau of Justice Statistics estimated that more than half of all jail and prison inmates nationwide had mental health problems such as depression, mania or a psychotic disorder.
But the new APA study failed to uncover any patterns linking criminality with mental illness over time. In fact, two-thirds of the defendants who committed crimes directly attributable to their symptoms had committed other offenses for reasons unrelated to mental illness.
Five researchers from universities across the country examined 143 offenders who were defendants in a mental health court in Minneapolis, Minn. Of the 429 crimes committed by the defendants, only 3% were found to be directly related to symptoms of major depression, 4% to symptoms of schizophrenia and 10% to symptoms of bipolar disorder, the study found.
“When we hear about crimes committed by people with mental illness, they tend to be big headline-making crimes so they get stuck in people’s heads,” lead research Jillian Peterson said in an APA news release. “The vast majority of people with mental illness are not violent, not criminal and not dangerous.”
A vast majority of defendants in the study had problems with substance abuse, but the researchers did not examine the possible relationship between substance abuse and mental illness in the offenders’ commission of crimes. The study, which was published in April 2014, did not include defendants who had committed violent crimes.
Peterson and her co-authors said their findings also raise doubts about the effectiveness of mental health treatment in reducing the likelihood that defendants will reoffend. Instead, they suggest that programs aimed at reducing recidivism should target a wider range of factors, including antisocial traits. Additionally, re-entry programs should focus on basic needs such as housing, substance abuse treatment and employment assistance.