"Without losing sight of the larger perspective that most who are violent are not mentally ill, and most of the mentally ill are not violent, our message is that mental health providers, lawyers and the public should be made aware that some unmedicated patients do pose an increased risk of violence," wrote researchers led by Dr. Ira Glick, from Stanford University's School of Medicine.
Glick's team studied 35 mass shooting cases that occurred in the United States between 1982 and 2019 and involved shooters who survived and were brought to trial.
Analysis of various sources of medical evidence on the mass shooters showed that 28 had mental illness diagnoses. Eighteen had schizophrenia and 10 had other diagnoses including bipolar disorder, delusional disorder, personality disorders and substance-related disorders.
Of the 28 shooters with a mental illness diagnosis, none were medicated or received other treatment for their disorders prior to their crimes, according to the study published recently in the Journal of Clinical Psychopharmacology.
Glick and his colleagues also examined 20 mass shooters who died at the crime scene and found that eight had schizophrenia, seven had other mental health diagnoses, and five had unknown diagnoses. None were receiving appropriate medications.
The investigators pointed out that despite the high frequency of mass shooting events in the United States, there has been almost no medical research on the nature and incidence of mental illness among people who commit these crimes.
"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," the authors noted in a Stanford news release.
"We need to reduce the stigma associated with these diseases to enable patients to receive appropriate and adequate psychiatric medication and other treatments," they added, "by actually talking to patients and their significant others, we have the opportunity to save lives."