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Study Finds Mass School Shootings Are Not Caused by Mental Illness

Data reveal psychosis and other serious psychiatric illness absent in the majority of perpetrators

by Columbia University Irving Medical Center
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A research team at Columbia University Irving Medical Center and the New York State Psychiatric Institute (NYSPI) examining 82 mass murders that occurred at least partially in academic settings throughout the world, found that most mass murderers and mass shooters did not have severe mental illness.

The study, led by Ragy R. Girgis, MD, and Gary Brucato, PhD, associate research scientist, also found that most mass murderers used firearms, and semi- or fully-automatic firearms most commonly. Among incidents of mass school murder not involving firearms, stabbing was the most common method.

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The research, published online in the Journal of Forensic Sciences, according to study authors, is largest analysis ever conducted on mass school shootings.

“Our findings suggest that mass school shootings are different from other forms of mass murder, and that they should be looked at as a distinct phenomenon,” said Girgis, director of the Center of Prevention and Evaluation (COPE), a research clinic at Columbia/NYSPI specializing in the study and treatment of young adults at high risk for schizophrenia and other psychoses. “To prevent future mass school shootings, we need to begin to focus on the cultural and social drivers of these types of events, such as the romanticization of guns and gun violence, rather than on individual predictors.”

To conduct their study, the researchers analyzed data from the Columbia Mass Murder Database (CMMD), developed by the COPE team to gain much-needed insight into the relationship between serious mental illness and mass shootings. Creating the CMMD involved extensive review of 14,785 murders publicly described in English in print or online, occurring worldwide between 1900 and 2019.

For the mass school shooting study, the researchers isolated cases of mass murder perpetrated at least in part at schools, colleges, and universities and categorized them by location (within or outside of the US), and whether firearms were used.

Of the 82 incidents of mass murder involving academic settings:

  • Nearly half (47.6 percent) and most involving firearms (63.2 percent) were US-based 
  • Consistent with previous reports, perpetrators of mass shootings involving academic settings are primarily Caucasian (66.7 percent) and male (100 percent)
  • Severe mental illness (e.g., psychosis) was absent in the majority of perpetrators; when present, psychotic symptoms are more associated with mass murders in academic settings involving means other than firearms
  • About half (45.6 percent) of mass school shootings ended with the perpetrator's suicide

Co-author Paul S. Appelbaum, MD, the Elizabeth K. Dollard Professor of Psychiatry, Medicine and Law at Columbia, said that identifying mental illness as a primary cause of violence is misleading. 

“The findings strongly suggest that focusing on mental illness, particularly psychotic illness, when talking about mass school shootings risks is missing other factors that contribute to the vast majority of cases, as well as exacerbating the already widespread stigma surrounding severe mental illness,” said Appelbaum.

Noting that almost half of mass shooters took their own lives at the scene, the authors hypothesize that perpetrators may see themselves as engaging in some form of final act.

The researchers hope that the findings will help lawmakers and law enforcement officials better understand the phenomenon of mass school shootings, as well as how mass school shootings differ from other forms of mass murder. The authors also emphasize that these data cannot be used to predict behavior on an individual level.

- This press release was originally published on the Columbia University Irving Medical Center website