“Repeat after me: Mass shooters are not disproportionately mentally ill.”

This is the opening line of a meme that’s been circulating in the aftermath of the shooting in Parkland, Fla.

But this and other efforts to downplay the role of mental illness in mass shootings are simply misleading. There is a clear relationship between mental illness and mass public shootings.

At the broadest level, peer-reviewed research has shown that individuals with major mental disorders (those that substantially interfere with life activities) are more likely to commit violent acts, especially if they abuse drugs. When we focus more narrowly on mass public shootings — an extreme and, fortunately, rare form of violence — we see a relatively high rate of mental illness.


According to our research, at least 59% of the 185 public mass shootings that took place in the United States from 1900 through 2017 were carried out by people who had either been diagnosed with a mental disorder or demonstrated signs of serious mental illness prior to the attack. (We define a mass public shooting as any incident in which four or more victims are killed with a gun within a 24-hour period at a public location in the absence of military conflict, collective violence or other criminal activity, such as robberies, drug deals or gang turf wars.)

Mother Jones found a similarly high rate of potential mental health problems among perpetrators of mass shootings — 61% — when the magazine examined 62 cases in 2012.

Both rates are considerably higher than those found in the general population — more than three times higher than the rate of mental illness found among American adults, and about 15 times higher than the rate of serious mental illness found among American adults.

It’s possible for mass public shootings to be both a gun problem and a mental health problem.


And yet this nuance often gets lost in mainstream news reports. In a story that largely suggested mass murderers are not “insane,” the New York Times cited research showing that, in fact, mass murderers are nearly 20 times more likely to have a “severe” mental illness than the general population.

According to our research, only one-third of the people who have committed mass shootings in the U.S. since 1900 had sought or received mental health care prior to their attacks, which suggests that most shooters did not seek or receive care they may have needed.

This treatment gap is underscored by evidence showing that the U.S. has higher rates of untreated serious mental illness than most other Western countries. Additional research shows that the gap is even larger for males, who have committed 99% of the country’s mass public shootings.

Although the link between mass shootings and mental illness has only recently gained widespread recognition, the correlation itself is longstanding. Indeed, we see it in some of the earliest such shootings in the U.S. Gilbert Twigg, who opened fire on a concert crowd in Winfield, Kan., in 1903, killing nine, had displayed signs of paranoia beforehand. Howard Unruh, who shot and killed 13 people in Camden, N.J., in 1949, was later diagnosed with paranoid schizophrenia. (Both were also Army veterans who had seen combat.)


One of the primary reasons some are reluctant to establish the link between mass shootings and mental illness is a fear that it will lead to the stigmatization of such disorders. This concern is valid. The vast majority of people with mental disorders are not violent, after all.

Conversely, some have insisted — wrongly, in our opinion — that mass public shootings are strictly a mental health problem rather than a gun problem. They, too, are on the wrong side of the evidence. It’s possible for mass public shootings to be both a gun problem and a mental health problem.

Increasing access to mental health care may reduce mass public shootings. But while such events are more commonplace than they should be, the reality may be that they’re still too rare to develop and implement policies that reduce their incidence or severity specifically.

Policymakers should therefore focus on strategies that have shown promise in reducing gun violence in general, like a federal universal background check.


Because there’s still a lot we don’t understand about mass shootings, we need to invest in research to develop evidence-based solutions. In the meantime, the media should stop glorifying this violence. In the midst of our tribal hyperpartisanship, the debate over mass shootings is doomed to continue ignoring facts. We won’t make any progress until those on the mental health side and those on the gun side find common ground that’s rooted in empirical reality.

Grant Duwe is research director for the Minnesota Department of Corrections and the author of “Mass Murder in the United States: A History.” Michael Rocque is a professor of sociology at Bates College.

Follow the Opinion section on Twitter @latimesopinion or Facebook