Are Mass Murderers Insane? Usually Not, Researchers Say<br />Analyzing his database, Dr. Stone has concluded that about 65 percent of mass killers exhibited no evidence of a severe mental disorder; 22 percent likely had psychosis, the delusional thinking and hallucinations<br />that characterize schizophrenia, or sometimes accompany mania and severe depression.<br />About one in five are likely psychotic or delusional, according to Dr. Michael Stone, a forensic psychiatrist<br />at Columbia University who maintains a database of 350 mass killers going back more than a century.<br />“The majority of the killers were disgruntled workers or jilted lovers who were acting on a deep sense of injustice,”<br />and not mentally ill, Dr. Stone said of his research.<br />Even if spree killers have committed domestic violence disproportionately more often —<br />and this assertion is in dispute — the vast majority of men who are guilty of that crime never proceed to mass murder.<br />The overall rate of any psychiatric history among mass killers — including such probable diagnoses as depression, learning disabilities or A. D.H. D.<br />About two-thirds of this group had faced “long-term stress,” like trouble at school or keeping<br />a job, failure in business, or disabling physical injuries from, say, a car accident.<br />In a 2016 analysis of 71 lone-actor terrorists and 115 mass killers, researchers convened by the Department of<br />Justice found the rate of psychotic disorders to be about what Dr. Stone had discovered: roughly 20 percent.
