In the aftermath of a mass casualty event like Tuesday's shooting in Uvalde, Texas, blame swirls, often landing on one frequent victim: mental illness. However, years of research show that mental illness does not play a role in the vast majority of gun violence.
In a press conference Wednesday, Texas Gov. Greg Abbott said that the 18-year-old gunman had a "mental health challenge." However, the shooter who killed 19 students and two teachers has no known or diagnosed mental health issues or criminal history.
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For researchers and experts in the fields of psychology and public health, Abbott's remarks and the response assuming the gunman was mentally ill aren't unusual.
"When horrible events happen that are unfathomable to our minds, we look for answers, and so one answer is that there must be something terribly wrong to lead somebody to act in such a way," said Dr. Rebecca Brendel, president of the American Psychiatric Association. "(But) what we know is that persons with mental illness are much less likely to commit acts of violence than others."
Lori Post, Ph.D., director of the Buehler Center for Health Policy and Economics at the Northwestern University School of Medicine, expressed a similar sentiment to NBC News: “There is no evidence the shooter is mentally ill, just angry and hateful. While it is understandable that most people cannot fathom slaughtering small children and want to attribute it to mental health, it is very rare for a mass shooter to have a diagnosed mental health condition.”
U.S. & World
Mass Shootings in the U.S. Since 1982
Incidents where 3 or more people were killed, not including the shooter.
Source: Mother Jones, NBC reporting
Last updated: May 25, 2025
Research on gun violence and mental illness
Statistics on mental illness and gun ownership are difficult to find, according to Lauren Khazem, Ph.D., a professor at Ohio State University who specializes in trauma therapy and suicide prevention research, due to the Dickey Amendment, which from 1996 to 2019 barred the Centers for Disease Control and Prevention from using federal funding to "advocate or promote gun control."
"Because of that, we're really lacking a lot of information related to firearm ownership and outcomes related to that, but what we do know from the limited research that's out there is ... most people who carry out mass murders don't have a diagnosed mental health condition," Khazem said.
Jeffrey Swanson, Ph.D. — a leading researcher in the field who has authored over 240 publications on the intersection of violence and mental illness and helps develop policies to help people with mental illnesses while reducing gun-related injuries and deaths — has conducted much of the research Khazem referred to.
Swanson called those who have a mental illness and commit a mass casualty shooting a "very small and atypical group."
"If you're referring specifically to public mass shooters, a lone individual who goes out and shoots people in a public place and more than four die, about 25% of those shooters have a pre-incident mental illness," Swanson told TODAY.
He also addressed an often-cited statistic that 4% of mass shooters have mental illness, a number that he said is "halfway correct" and is based on research he published in the '90s. He clarified that just 4% of community violence can be attributed to the 14 million people in the United States diagnosed with a severe mental illness like schizophrenia, bipolar disorder and major depression.
With about 14 million people in the United States having been diagnosed with a serious mental illness, Swanson emphasized that the number of people with mental illness who commit a mass shooting is a "very small contributor" to the rates of gun violence in the United States.
"Even if you were to do everything possible to eliminate mental illness, you'd really only be addressing around 3% of the violence in this country," said Dr. Reena Kapoor, professor of psychiatry at the Yale School of Medicine.
What drives mass casualty shootings and gun death, said Swanson and other experts interviewed for this story, is access to guns.
"We have way more gun deaths by a mile than these other (high-income) countries, and they don’t have a higher rate of mental illness or crime," Swanson said, noting the U.S. has similar rates of untreated psychiatric illness and mental health spending per capita to other countries.
"Mass shootings are a uniquely American problem," added Kapoor. "Any reasonable person would think maybe that has something to do with the big difference in our gun laws and those in other countries, and that access to very dangerous weapons is much easier here than anywhere else in the world."
This story first appeared on TODAY.com. More from TODAY: