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Untreated Psychiatric Illness Is Behind Many Mass Shootings, A New Study Says


Tom Hale

Senior Journalist

clockJun 11 2021, 14:41 UTC
Stephen Paddock.

PARIS, FRANCE - OCT 3, 2017: A newspaper shows Stephen Paddock, the perpetrator of the 2017 Las Vegas Strip shooting. Image credit: Hadrian/

The first five months of 2021 saw over 240 mass shootings in the US. That’s according to the Gun Violence Archive, which defines a mass shooting as one with four or more people injured or killed, not including the perpetrator. In fact, the recent spate of mass shootings seen over the past three months since the US “re-opened” from lockdown is said to be one of the worst in US history.

While no single factor can explain this broad range of tragic events, a new study argues that one factor can be linked to the majority of mass shooters: untreated and unmedicated psychiatric illness. 


This finding is far from definitive — earlier this year, a separate study concluded that mental illness isn't a factor in most mass shootings. This latest piece of research, just like those before it, is simply a snapshot of this deeply complex issue that continues to defy a full explanation. 

As reported in the Journal of Clinical Psychopharmacology this week, scientists at Stanford University School of Medicine and the Icahn School of Medicine at Mount Sinai Hospital sifted through the Mother Jones Mass Shootings Database, 1982 – 2021 — which they claim was one of the most comprehensive databases on the subject — to carry out a retrospective, observational study of mass shooters.

They identified 115 people who had committed a mass shooting in the US from 1982 to 2019. From this, they focused on 35 cases where the assailant survived, underwent criminal proceedings, and there was a suitable amount of information available. 

Out of the 35 shooters, 32 showed clear signs and symptoms that fit the scientific diagnostic criteria for a clinical psychiatric disorder. Eighteen of the perpetrators had schizophrenia, while 10 had other diagnoses including bipolar disorder, delusional disorder, personality disorders, and substance-related disorders. In just four cases they found no psychiatric diagnosis (Not enough information was available to make a diagnosis in the remaining three cases).


Of the 28 surviving assailants with a psychiatric diagnosis, none had received medication or treatment before the shooting. 

None of this is to suggest that mental illness always equates to violence or mass shootings; violence is primarily carried out by people who are not mentally ill and most of the mentally ill are not violent. Furthermore, it does not indicate that mental illness is the sole driver of mass shootings. The cause of mass shootings is multi-faceted and diverse, with different explanations ranging from extreme ideological beliefs and socio-economic factors to easy access to firearms, and so on. 

However, the research does indicate how better mental health services and psychiatric care have the very real potential to reduce senseless deaths from mass shootings. 

"The psychiatric disorders seen in perpetrators of mass shootings are serious brain illnesses - as much in need of proper diagnosis and treatment as heart disease or any other medical condition," Dr Ira D Glick, lead study author from the Stanford University School of Medicine, said in a press release. "We need to reduce the stigma associated with these diseases to enable patients to receive appropriate and adequate psychiatric medication and other treatments. By actually talking to patients and their significant others, we have the opportunity to save lives."

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