Crimes and Mental Illness: The Link Isn’t As Strong As You Think


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Mental illness does not necessarily lead to crime. Image by mzacha.

Mental illness does not necessarily lead to crime. Image by mzacha.

People with mental illness have long gotten a bad rap as being violent and dangerous. The media seem to emphasize the connection between mental illness and criminality, especially when a high profile crime is committed by someone with a diagnosis of mental illness. In reality, the link is tenuous, as demonstrated by a recent study.

Mental Illness and Crime

The study, led by Jillian Peterson, Ph.D., who is an Assistant Professor of Criminal Justice at Metropolitan State University, analyzed 429 crime events. The perpetrators of the crimes were interviewed about their symptoms of schizophrenia, depression and bipolar disorder, as well as their criminal history.

An analysis of the results revealed that only 7.5 percent of the crimes were directly related to symptoms of mental illness. In other words, immediately before they commit crimes, most people do not experience serious symptoms, such as hallucinations, that influence their behavior.

Crime: A Social Issue

Mental illness and violence have long been linked in the minds of the public. In 2003, Heather Stuart, a researcher at Queen’s University in Canada, published an overview of violence and mental illness in the World Psychiatry journal. She explained that mental illness is not a precursor to violence. Instead, the most common contributors to violent behavior are socio-economic factors, such as poverty.

Stuart explained that when people with mental illness do perpetrate violent acts, their most likely targets are family and friends within the home setting. The violence usually emerges from a background of hostility and poor family relationships, indicating that poor social and living conditions, more than mental illness, create fertile ground for violent behavior.

Furthermore, people with mental illness are far more likely to be victims, rather than perpetrators, of crime. According to a study led by Urara Hiroeh that was published in the medical journal The Lancet, people with mental health disorders are at increased risk of death by homicide.

Another study, led by Dr. Virginia Aldige Hiday of the North Carolina State University, exposed the alarming statistic that people with severe mental illness are 2 ½ times more likely to be attacked, mugged or raped than people in the general population.

Substance Abuse Can be Deadly

One factor evident in nearly every study on the subject is substance abuse. On their own, and especially in combination with a mental illness, drug and alcohol abuse frequently lead to violence and crime.

Two studies led by Dr. Seena Fazel of the University of Oxford in England demonstrated the lethality of the combination of mental illness and substance abuse. In 2010, Fazel and colleagues published a study showing that while people with Bipolar Disorder have a negligible risk of committing a violent crime, those who have Bipolar Disorder and are substance abusers are at far higher risk.

Similarly, their 2009 study showed that people diagnosed with both schizophrenia and substance abuse have a 28.3 chance of committing a violent crime, compared with a 3.4 chance for those in the general population.

The British Crime Survey confirms these studies with anecdotal evidence. Seventeen percent of the victims of violent crimes believed that their offender was under the influence of drugs, and almost half of the victims of violent crimes believed that their offender was influenced by alcohol. Meanwhile, only one percent of the victims surveyed believed that a mental illness led the offender to attack.

Effective Medications

Last week, Dr. Fazel of Oxford University published a new, eye-opening study about mental illness and crime. He and his colleagues studied the effect of anti-psychotic medications and mood stabilizers on the rate of violent crimes performed by people diagnosed with psychiatric disorders. They reviewed the records of 82,647 people who were prescribed mood stabilizers (which typically treat Bipolar Disorder) and anti-psychotics (which usually treat Schizophrenia and other thought disorders).

The researchers compared the rates of violent crimes committed by those who took medication with the rates of those who did not receive medication to treat their psychiatric disorders. The results suggest that psychotropic medication do indeed curb violent criminality, with a 45% decrease in convictions for violent crimes while patients were taking their medications.

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