In discussions of mass shootings, the topic of mental illness regularly comes up, often paired with pleas to improve mental health services instead of or in addition to gun control measures. While the mental health care system in the United States is abysmal and in desperate need of more funding, this is a bit of misleading connection to draw.
For one thing, mass shootings are a tiny percentage of the overall homicide problem and should not be blown out of proportion. But more importantly, our violent crime problem really has little to do with mental illness. Columbia’s Paul Appelbaum and Duke’s Jeffrey Swanson concluded that “only 3%-5% of violent acts are attributable to serious mental illness, and most do not involve guns.” Similarly, a study in Sweden found that only 5.2 percent of violent crimes were committed by people with serious mental illness.
Nor does this picture change when you look at just mass shootings and mass murders, not all violence or all homicides. Michael Stone, a psychiatrist at Columbia who maintains a database of mass shooters, wrote in a 2015 article that only 52 out of the 235 killers in the database, or about 22 percent, were mentally ill. “The mentally ill should not bear the burden of being regarded as the ‘chief’ perpetrators of mass murder,” Stone concludes.
Northeastern University criminologist James Alan Fox, a frequent writer on mass murder and mass shootings, and fellow researcher Emma Fridel analyzed a Stanford Geospatial Center database compiling shooters who killed four or more people since 1966. Of the 88 shooters who met that criteria, only 14.8 percent had been diagnosed with a psychotic disorder. And even for them, it’s hard to say with any certainty that mental illness caused or contributed to their shooting.
That doesn’t mean that certain types of mental illness aren’t risk factors for violence. A National Institute of Mental Health study found that 16 percent of people with serious mental illness (such as schizophrenia or bipolar disorder) commit a serious act of violence in their lifetime, compared with 7 percent of the general population. But anxiety disorders didn’t increase one’s risk of committing violence at all.
Much more important as a factor is drug and alcohol abuse; Cornell psychiatrist Richard Friedman notes that the same NIMH study found that “people with no mental disorder who abused alcohol or drugs were nearly seven times as likely as those without substance abuse to commit violent acts.” A Mayors Against Illegal Drugs analysis of mass shootings found a much stronger connection to domestic violence than to mental illness.