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Mass Shooters: A Systematic Psychiatric Study

About 87% were misdiagnosed and wrongly treated or undiagnosed and untreated.

Key points

  • A new study indicates there is an association, not a causal relationship, between mass shooting and undiagnosed, untreated psychiatric illness.
  • Researchers found psychiatric illnesses including schizophrenia, mood disorders, delusional disorder, severe personality disorders and others.
  • Individuals who suffer from psychiatric illness and get appropriate treatment are not any more violent than the rest of the population.

It's every American's worst nightmare: a mass shooting. The subject of mental health is brought up every time, and yet there is a dearth of psychiatric research since perpetrators often die in the incident and those who survive are mired in legal repercussions.

Nina Cerfolio, MD, Clinical Assistant Professor at Icahn School of Medicine at Mount Sinai in New York, wanted to look deeper into the underlying psychiatric, psychosocial, and psychodynamic data. She conducted what she says is the first-ever systematic psychiatric research on this complex topic, with co-authors Ira Glick, MD, Danielle Kamis, MD, and Michael Laurence, JD. Their study published online with open access in February 2022 and is included in the September 2022 print issue of the Psychodynamic Psychiatry Journal.

Maurício Mascaro/Pexels
Researchers found a high prevalence of undiagnosed psychiatric illness in mass shooters.
Source: Maurício Mascaro/Pexels

Cerfolio's team focused primarily on the ample forensic psychiatric assessments done in prison on the 35 assailants who survived incidents in the United States between 1982 and 2019*. They combed through psychiatric evaluations from the judicial proceedings, interviewed the forensic psychiatrists who conducted direct assessments and examined the shooters' backgrounds. Additionally, they randomly selected 20 deceased shooters from that same time period and analyzed all the information they could find.

After gathering all the clinical and background information, they then determined whether the perpetrators could be diagnosed with psychiatric illness by utilizing standardized instruments such as the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the Sheehan MINI standardized scale (which assesses functional impairment in work, social/leisure activities and family life).

4 key takeaways

Their findings showed a high prevalence of undiagnosed psychiatric illness in mass shooters:

  • The majority of surviving shooters (87.5%) had misdiagnosed and incorrectly treated, or undiagnosed and untreated, psychiatric illness. Researchers found psychiatric illnesses including schizophrenia, mood disorders, delusional disorder, severe personality disorders, substance-related disorders and PTSD. There was insufficient information in three cases.
  • A clinical misdiagnosis and mistreatment of pre-pubertal, early-onset schizophrenia was associated with the worsening of many of these assailants’ psychotic symptoms.
  • Most perpetrators studied experienced profound estrangement not only from families, friends and classmates but most importantly from themselves.
  • Being marginalized and interpersonally shunned rendered them more vulnerable to their un/mistreated psychiatric illness and to radicalization online, which fostered their violence.

"Each mass shooting is unique and occurs due to a synthesis of psychology, personal circumstances and environment: it is essential to clarify that we are not stating that psychiatric illness causes these acts of violence," states Cerfolio. "Rather, our findings suggest there is a complex interaction between biological, psychological and sociological factors, and an association — not a causal relationship — between mass shooting and undiagnosed, untreated psychiatric illness. It's important to remember that most individuals who suffer from psychiatric illness and get appropriate treatment are not any more violent than the rest of the population."

The most common diagnosis: schizophrenia

Cerfolio et al. (2022) found that 18 of the 35 surviving shooters had schizophrenia, overwhelmingly the most common diagnosis. In 15 of 20 cases in which the assailant died, the researchers determined that eight had schizophrenia. None were on appropriate medication.

"Many of our adolescent shooters prior to the massacre had been misdiagnosed with Attention Deficit Disorder, Major Depression Disorder or Autism Spectrum Disorder, " says Cerfolio.

Why weren't they diagnosed correctly? "The DSM-5 prevents a definitive diagnosis of schizophrenia before 18 years of age because the adolescent brain is still developing," Cerfolio explains. "However there are identifiable early onset schizophrenia symptoms. So it is extremely important to provide an adolescent experiencing early onset symptoms such as hallucinations and delusions with crucial psychiatric treatment and antipsychotic medication. The earlier treatment is initiated the better the clinical outcome to stop their psychotic symptoms."

What this means going forward

What can American society, especially mental health professionals, glean from this study going forward? The details hold some important lessons:

  1. "While there are complex reasons why a person may not be diagnosed, there remains an urgent need to decrease the stigma of mental illness to enable those suffering from psychiatric illness to be more respected to receive care," Cerfolio says. (More on this below.)
  2. Awareness of the possibility of under-diagnosis of mental disorders, particularly in young males, is crucial for both the professional community and parents. Vulnerable individuals need help in order to seek, access and receive the psychiatric support they need and deserve.
  3. Cerfolio says this study underscores how important it is for mental health professionals to refer a person struggling with psychosis for medical evaluation by a board-certified psychiatrist who can prescribe life-saving psychiatric medications.

Stigma is still the largest impediment

As is often reported in the aftermath of a mass shooting, many perpetrators have a history of being marginalized or bullied; this study found that many also suffered neglect or abuse. Cerfolio says they felt worthless, had no place in the world and nothing to offer anyone. They are also often extremely smart and thus were able to hide their psychosis to avoid being labeled with a mental illness. That is, until a life crisis occurs which is often the triggering event that provokes their violence.

Kayley Dlugos/Pexels
Many perpetrators have a history of being marginalized or bullied.
Source: Kayley Dlugos/Pexels

Family members can also be afraid of the stigma. The study highlighted one case where the family of a 15-year-old school shooter had concealed his psychotic symptoms from a treating psychologist.

“Given the social stigma of mental illness, these mass shooters did not receive proper psychiatric care until they were incarcerated,” says Cerfolio. “The ironic tragedy with some of these assailants was that their brain illness responded well to antipsychotic medication while they were incarcerated and their violent acts might have been prevented if they had received proper psychiatric medication prior to their shooting spree.”

Cerfolio warns of the larger societal issue that is a contributing factor: “Many people focus on diagnoses, but we also must start focusing on people who are isolated and have been discarded by society, often even by their own family. They don’t know how to get help, or can’t access help on their own. Mass shootings will continue to happen in America until we address this epidemic as a society.”


Cerfolio, N. E., Glick, I., Kamis, D., & Laurence, M. (2022). A Retrospective Observational Study of Psychosocial Determinants and Psychiatric Diagnoses of Mass Shooters in the United States. Psychodynamic Psychiatry, 1–16.

*Researchers used the Mother Jones database to determine perpetrator inclusion in the study.

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