Mass Shootings and Mental Illness

There have already been more than 300 mass shootings in the United States this year—the latest at a 4th of July parade in the Highland Park suburb of Chicago that left seven people dead and dozens injured. As the nation reckons with these increasingly common public massacres, many blame mental illness as the fundamental cause.

The reality is that people with mental illness account for a very small proportion of perpetrators of mass shootings in the U.S., says Ragy Girgis, MD, associate professor of clinical psychiatry in the Columbia University Department of Psychiatry and the New York State Psychiatric Institute.

In 2021, Dr. Girgis, an expert in severe mental illness, and colleagues from Columbia’s Center of Prevention and Evaluation authored the first report on mass shootings from the Columbia Mass Murder Database (CMMD), which examined the relationship between serious mental illness and mass shootings.

Columbia Psychiatry News spoke with Dr. Girgis about the role of mental illness in mass shootings, the motivations behind mass murder, why the perpetrators of mass violence use guns, and more.

Are people with mental health disorders more likely to commit mass shootings or mass murder?

The public tends to link serious mental illnesses, like schizophrenia or psychotic disorders, with violence and mass shootings. But serious mental illness—specifically psychosis—is not a key factor in most mass shootings or other types of mass murder. Approximately 5% of mass shootings are related to severe mental illness, and although a much larger number of mass shootings (about 25%) are associated with non-psychotic psychiatric or neurological illnesses, including depression, and an estimated 23% with substance use, in most cases these conditions are incidental.

Additionally, as we demonstrated in our paper, the contribution of mental illness to mass shootings has decreased over time. The data suggest that while it is critical that we continue to identify those individuals with mental illness and substance use disorders at high risk for violence and prevent the perpetration of violence, other risk factors, such as a history of legal problems, challenges coping with severe and acute life stressors, and the epidemic of the combination of nihilism, emptiness, anger, and a desire for notoriety among young men, seem a more useful focus for prevention and policy than an emphasis on serious mental illness, which leads to public fear and stigmatization.

Why does the public erroneously link mental illness with mass shootings and with violence in general?

A lot of people who aren’t experts in mental illness tend to equate bad behavior, and often immorality, with mental illness. These are a false equivalence. I think it's incumbent on us, especially when we're talking about something as horrible as mass shootings, to make sure other people understand that all bad behavior, and certainly not evil and pure psychopathy, is not the same as mental illness.

What is the Columbia Mass Murder Database?

The Columbia database, compiled by researchers at the New York State Psychiatric Institute and the Columbia University Irving Medical Center, is the largest catalog of mass shootings and mass murder in the world. We have approximately 1,800 entries, including any mass shooting or murder reported between 1900 and 2019 worldwide that resulted in at least three deaths (not including the perpetrator).

The major findings from our database are that the vast majority of mass shootings and mass murder are committed by people without mental illness, and certainly not psychotic illness, and when a person with severe mental illness commits a mass murder, they’re much less likely to use firearms than other methods, such as arson or knives.

How is CMMD different from other databases tracking this topic?

The CMMD is different because we examined mass murder before the modern period until the present to assess changes over time, included mass murder committed by means other than firearms so we could examine what is specific about mass shootings, and collected information on mass shootings and mass murder committed worldwide. We were comprehensive by collating names and events reported in all types of databases, including popular databases, but we made sure that our data were robust by only keeping names and events, and information on these events, included in reputable news sources, as well as court and police records.

Why do people use guns when they when they commit mass murder?

There's solid evidence that nearly half of all mass shootings are associated with suicide by perpetrator, or what they call “suicide by cop.” Guns are the most successful method of killing oneself.So, one main reason people choose guns is they want to die. In about 30% of mass shootings, perpetrators kill themselves with their own gun; about 10% are suicide by cop. However, while guns are the most effective method of suicide, they’re not as effective at killing a large number of other people. Mass murder committed with means other than firearms, such as bombing, arson, vehicles, even stabbings, is about two and a half times more deadly than mass murder committed with firearms.

Another reason people use firearms to carry out mass shootings (aside from availability) is our cultural romanticization of violence. As a result, the movie, television, music, and video game industries will have to play a role in any efforts to decrease gun assaults.

What tends to be the motivations behind mass shootings?

First, understand that mental illness as the primary cause of any mass murder, especially mass shooting, is uncommon. Half of all mass shootings are associated with no red flags—no diagnosed mental illness, no substance use, no history of criminality, nothing. They’re generally committed by middle-aged men who are responding to a severe and acute stressor, so they're not planned, which makes them very difficult to prevent. So, we must look much further upstream.

This is why it is important to consider ways to manage gun availability, for example. The yearly prevalence of the incidence of mass murder was stable at about 7 per billion people, or seven mass shootings for every billion people, between 1900 and about 1970. Then between about 1970 and 2019, the incidence increased by four times, so now mass shootings occur about 28 times per billion people around the world. One might say that this is because of the availability of guns in general, and automatic weapons, in particular, especially in the U.S. where these weapons became more available to the general population during this time period. Mass murder committed with means other than firearms also grew, but at a slightly slower rate. The other thing that one must consider is that most mass shootings are committed with non-automatic weapons, making them the weapons of choice, and supporting the notion that gun availability is a primary contributor to method of mass murder.

You have said that the media’s publishing personal details about the perpetrators encourages violent behavior and is harmful. Would you also include the 24-hour cable news cycle and social media which cause news to spread much further and faster?

If we’re talking about the mass shooters that we hear the most about, such as school shooters and other individuals who commit such public crimes, we have examined a number of these cases and are seeing a pattern. As opposed to most mass shooters, these perpetrators tend to be younger males who are often nihilistic, empty, angry, feel rejected by society, blame society for their rejection, and harbor a strong desire for notoriety. They want to make their mark on the world that will elevate them to the status they believe they are entitled to and deserve.  

Sensationalized headlines, photographs, and breaking personal information about the shooters, victims, and acts themselves provide the notoriety perpetrators of mass shootings crave and can spark others to carry out similar acts. Refraining from publishing any personal information about mass shooters may be one of the easiest, quickest, and most effective interventions for decreasing mass shootings, especially school and other public shootings, which comprise about 10% of all mass shootings.

Is there a difference in violence committed by women vs. violence committed by men?

Mental illness makes more of a difference when we're talking about violence committed by women, who are responsible for about 5% to 8% of mass murder. This is because the mechanism by which mental illness and substances of abuse, when they are causative, contribute to violence is by impairing impulse control. Research has shown that the lack of impulse control caused by mental illness and substances has a greater effect on women than on men, likely because men, especially younger men, tend to already be quite impulsive. It is also important to note that when women perpetrate mass murder, they are much less likely to use firearms than other methods, consistent with our thesis that mental illness is minimally responsible for mass shootings.