01/28/2016 06:22 pm ET Updated Jan 28, 2017

The Role of Mental Illness in Gun Crime: Dispelling the Myth

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In the wake of the hundreds of mass shootings over the past couple of decades, the media has been teeming with conversations about mental illness. Newspaper headlines have propagated the notion that gun crime is strongly associated with mental illness, and that people who commit gun crimes suffer from mental illness.

As it turns out, only about 2 to 4 percent of gun crimes are attributable to mental illness (Fazel & Grann, 2006). In making this claim, however, it is important to first distinguish between mass shootings and "everyday" shootings.

Mass shootings are relatively rare events. A mass shooting involves a perpetrator indiscriminately killing four or more people (not including him- or herself) in a single incident, usually in a single location (Follman, 2012). In mass shootings, mental illness can and often does play a role in the perpetration of violence, but does not explain the full story behind them (e.g. Langman, 2009).

"Everyday" shootings are different from mass shootings. As the name suggests, this type of shooting occurs every day. "Everyday" shootings often involve gang violence, robbery or theft, domestic disputes, other violent crime, or substance abuse. Mental illness plays almost no role in the perpetration of "everyday" gun crime (e.g. Monahan & Arnold, 1996). The conflation of mass shootings and "everyday" shootings is problematic because it masks the differences in underlying causes and factors between the two types of gun crime. Mass shootings and "everyday" shootings are committed by different types of people for different reasons. When discussing the role of mental illness in gun crime, therefore, it is crucial to specify which type of crime is at play.

In his seminal work, Why Kids Kill: Inside the Minds of School Shooters, psychologist Peter Langman discusses the psychological factors involved in school shootings. He offers evidence that individuals who commit mass shootings tend to suffer from mental health issues. First, he notes that depression is highly prevalent among school shooters. Of the ten school shooters he analyzes in the book, nine suffered from depression. These shooters felt like failures in their lives and envied their peers who were happier and more successful than they were.

This envy gradually become anger and rage, which gradually turned to homicidal ideation. Furthermore, many of the shooters Langman analyzes experienced suicidal ideation in addition to homicidal ideation, and some of those who experienced suicidal ideation did in fact kill themselves after the mass shooting. In most of these cases, the suicidal ideation preceded the homicidal ideation. Much scholarly research supports the findings presented in Langman's book.

However, mental illness does not explain the whole story behind mass shootings. About 1 in 4 people in the United States have a diagnosable mental illness and most of them do not commit mass shootings. One of the principles of modern epidemiology is that one risk factor alone does not lead to a particular outcome, but rather a combination of risk factors together can result in an outcome.

In the case of mass shootings, we must consider mental illness not in isolation but as part of a larger picture. So, what sets those mentally ill individuals who commit mass shootings apart from those mentally ill individuals who do not commit any acts of violence? According to the research, risk factors for gun crime perpetration include the availability of and access to guns; lack of family and community support and validation; substance use and abuse; noncompliance with psychiatric medications; and a preoccupation with violence, weapons, war, and violent video games (Langman, 2009; Meloy et al., 2001; Meloy et al., 2004).

Far more common than mass shootings are "everyday" shootings, in which mental illness plays almost no role. According to the National Center for Health Statistics, of the nearly 120,000 gun homicides that took place between 2001 and 2010, very few were committed by people with mental illness. In fact, research has found that people with mental illness are more likely to be victims of gun crime than perpetrators. Perhaps the best-known researchers who have explored this topic are John Monahan and Jean Arnold. In their review of epidemiological studies examining the relationship between gun crime and mental illness, they found that no such relationship exists. Instead, situational factors, such as substance use, interpersonal conflict, and access to guns, are largely responsible for the perpetration of gun crime.

Holding onto the false belief that mental illness drives gun crime has several adverse effects. This belief continues to stigmatize people with mental illness. It has also led to problematic laws and policies, such as the creation of special statuses for the extended detention of prisoners with mental illness, the imposition of a tort liability on psychologists and psychiatrists who do not foresee the violence of their patients, and the creation of a "direct threat" exception to employment protections guaranteed by the Americans with Disabilities Act.

To turn conversations about gun crime into conversations about mental health and mental illness is to avoid the true issues underlying gun crime. Gun crime should be thought of not as a problem of a select group of individuals, but rather as a problem driven by a combination of situational, social, and cultural factors along with individual factors in rare cases. Programs targeting the situational, social, and cultural factors leading to gun crime rather than the individual factors that contribute to only a small fraction of gun crimes would play a much greater role in ending the gun violence epidemic.

Centers for Disease Control and Prevention, 2013. Leading causes of death reports.
Fazel, S. & Grann, M. (2006). The population impact of severe mental illness on violent crime. The American Journal of Psychiatry, 163(8): 1397-1403.
Follman, M. (2012). What exactly is a mass shooting? Mother Jones. Retrieved December 1, 2013 from
Langman, P. (2009). Why Kids Kill: Inside the Minds of School Shooters. New York, NY: Palgrave Macmillan.
Meloy, J.R., Hempel, E.G., Mohandie, K., Shiva, A.A., & Gray, B.T. (2001). Offender and offence characteristics in a nonrandom sample of adolescent mass murderers. Child & Adolescent Psychiatry, 40(6): 719-728.
Meloy, J.R., Hempel, E.G., Gray, B.T., Mohandie, K., Shiva, A.A., & Richards, T.C. (2004). A comparative analysis of North American adolescent and adult mass murderers. Behavioral Sciences and the Law, 22(3): 291-309.
Monahan, J. & Arnold, J. (1996). Violence by people with mental illness: A consensus statement by advocates and researchers. Psychiatric Rehabilitation Journal, 19(4): 67-71.