New Findings from the Columbia Mass Murder Database

Data from Columbia Mass Murder Database reveal psychosis and other serious psychiatric illness absent in the majority of perpetrators

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 psychiatric illnesses.

The study, led by Ragy R. Girgis, MD,  found that 100% of the mass killings were initiated by males (mean age 28) of whom 66.7% were Caucasian. Sixty-three percent of the murders involved firearms. While severe mental illnesses, such as psychotic disorders, including schizophrenia, were not present in the perpetrators of these events, it is notable that almost half of these mass shooters took their own lives at the scene, leading the authors to hypothesize that these perpetrators viewed themselves as engaging in some form of “final act.” 

The research, published online Oct. 27 in the Journal of Forensic Sciences, according to study authors, is the 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 Dr. 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%) were U.S.-based. 
  • Most involved firearms (63.2%), commonly semi- or fully-automatics.
  • Consistent with previous reports, perpetrators of mass shootings involving academic settings are primarily Caucasian (66.7%) and male (100%).
  • Severe mental illness (e.g., psychosis) was absent in the majority of perpetrators; when present, psychotic symptoms were more often associated with mass murders involving means other than firearms.
  • About half (45.6%) of mass school shootings ended with the perpetrator's suicide. 

Coauthor Paul S. Appelbaum, MD, the Elizabeth K. Dollard Professor of Psychiatry, Medicine and Law at Columbia, said that identifying psychiatric 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 Dr. Appelbaum.

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, and ways to identify youth who may be troubled though not necessarily schizophrenic or psychotic. The authors also emphasize that these data cannot be used to predict behavior on an individual level.


Carla Cantor

Director of Communications, Columbia Psychiatry
347-913-2227 |