In the wake of the Las Vegas massacre, politicians are once again promoting the politically expedient notion that better mental health care could stop such mass killings. Paul D. Ryan, the speaker of the House, said last week that “mental health reform is a critical ingredient to making sure that we can try and prevent some of these things from happening in the past.”



The public appears to share this view. A 2015 poll found that 63 percent of Americans blamed deficient mental health care rather than deficient gun regulations for these shootings.

It’s true that many mass murderers do have a mental disorder, typically a severe personality disorder or a psychotic illness. But this fact has almost no implication for how to stop them.

Why? First, a vast majority of these killers avoid the mental health care system. They are intent on murdering people, not on seeking help, and generally don’t see themselves as psychiatrically ill. Of the 92 documented mass killings from 1982 to 2017, only 15 percent of the perpetrators had any known previous contact with mental health professionals.