Mental illness is not a crime. But for those living with a severe, debilitating brain disorder, it can be a life sentence battling symptoms such as unpredictable mood swings, hallucinations, delusions or paranoia that sometimes can lead to bizarre behaviors, uncontrollable outbursts and even suicide. Suicide is the 10th leading cause of death in the United States. It accounts for the loss of more than 41,000 American lives each year, more than double the number of lives lost to homicide.

Are the mentally ill more violent?

The mentally ill are statistically more likely to be the victim of violent crime than an average person. They are also less likely to commit violent crimes, both in absolute terms and in numbers as perceived by crime victims. So: No, the mentally ill are less violent as a group than are average people.

The relationship between mental health and crime, as with that between the brain and crime, is one that is both complex and controversial. The media has, unfortunately, often represented this link in a negative way, leading to the perception that people committing certain types of offences are all mentally ill. This is, of course, far from the case.

Mental Illness Not Usually Linked to Crime, Research Finds

In a study of crimes committed by people with serious mental disorders, only 7.5 percent were directly related to symptoms of mental illness, according to new research published by the American Psychological Association.   

Researchers analyzed 429 crimes committed by 143 offenders with three major types of mental illness and found that 3 percent of their crimes were directly related to symptoms of major depression, 4 percent to symptoms of schizophrenia disorders and 10 percent to symptoms of bipolar disorder.

“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,” said lead researcher Jillian Peterson, PhD. “The vast majority of people with mental illness are not violent, not criminal and not dangerous.” 

The study was conducted with former defendants of a mental health court in Minneapolis. The participants completed a two-hour interview about their criminal history and mental health symptoms, covering an average of 15 years. The study, published online in the APA journal Law and Human Behavior, may be the first to analyze the connection between crime and mental illness symptoms for offenders over an extended period of their lives, said Peterson, a psychology professor at Normandale Community College in Bloomington, Minn.  

The study didn’t find any predictable patterns linking criminal conduct and mental illness symptoms over time. Two-thirds of the offenders who had committed crimes directly related to their mental illness symptoms also had committed unrelated crimes for other reasons, such as poverty, unemployment, homelessness and substance abuse, according to the research. “Is there a small group of people with mental illness committing crimes again and again because of their symptoms? We didn’t find that in this study,” Peterson said. 

In the United States, more than 1.2 million people with mental illness are incarcerated in jails or prisons, according to the federal Bureau of Justice Statistics. People with mental illnesses also are on probation or parole at two to four times the rate for the general population.

In addition to interviews with offenders, the researchers reviewed criminal history and social worker files to help rate crimes based on their association with symptoms of schizophrenia disorders (hallucinations and delusions), bipolar disorder (impulsivity and risk-taking behavior) or major depression (hopelessness and suicidal thoughts). The ratings were: no relationship between mental illness symptoms and the crime, mostly unrelated, mostly related or directly related.  

A crime could be rated as mostly unrelated or mostly related to mental illness symptoms if those symptoms contributed to the cause of the crime but weren’t solely responsible for it. For example, an offender with schizophrenia who was agitated because he heard voices earlier in the day later got into a bar fight, but he wasn’t hearing voices at the time of the altercation, so the crime was categorized as mostly related. 

Public opinion surveys suggest that many people think mental illness and violence go hand in hand. A 2006 national survey found, for example, that 60% of Americans thought that people with schizophrenia were likely to act violently toward someone else, while 32% thought that people with major depression were likely to do so.

In fact, research suggests that this public perception does not reflect reality. Most individuals with psychiatric disorders are not violent. Although a subset of people with psychiatric disorders commit assaults and violent crimes, findings have been inconsistent about how much mental illness contributes to this behavior and how much substance abuse and other factors do.

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