After the latest school shooting in Parkland, FL, when a young man was accused of shooting 17 people, the conversation immediately turned to mental illness. Nikolas Cruz, the defendant, is believed to have a history of mental illness, and as a result, his condition became a topic of discussion by politicians and the media alike.

The New York Times quotes John T. Monahan, a professor specializing in psychology and law at the University of Virginia:

“Two things typically happen in the wake of a mass shooting. First, politicians claim that mental illness is the major cause of violence in America. Then, advocates for people with mental illness respond by denying there is any relationship whatsoever between mental illness and violence. Both groups are wrong. Research shows that the association between mental illness and violence is not strong, but it does exist.”

Mental illness as a primary cause of gun violence is a common misconception

According to a poll conducted by CBS News one year after the shooting at Sandy Hook Elementary School, the majority of respondents believe mental health to be a primary cause of gun violence. 68% of respondents believe that improved mental health screening would prevent gun violence. This steeply contrasts against the reality of the data, which shows that only 1% of all gun homicides are linked to shooters with mental illness.

The intersection between mental illness and gun violence is much smaller than what politicians and lawmakers in mass media today would lead us to believe. In fact, when we do further research into the topic, we find several studies that substantiate this:

In a study of 235 mass shootings, only 22% of perpetrators were considered mentally ill

Contradictory to popular belief, people with mental illness are typically much more likely to harm themselves rather than others. Therefore, the real pressing issue among those with mental illness should be self-harm and self-injury rather than mass violence.

Mental health screening as a method of preventing gun violence is insufficient

In NPR’s interview with Jonathan Metzl, a psychiatrist and director of the Vanderbilt Center for Medicine, Health, and Society, the topic of using mental health screening as a method preventing further mass shootings:

CHANG (Host): First of all, I know that you take issue with this call from politicians that mental health professionals like you need to step up and help prevent gun violence. Why do you think that’s the wrong way to approach this?

METZL: Well, certainly we should all do everything we can to prevent gun violence, and I think that mental health expertise is an important part of the conversation. But the reason that I and other people in my position write against this is first of all because people with mental illness are not a particularly high-risk group for gun violence or for mass shootings.

People with mental illness being incorrectly associated with being at-risk for gun violence, so screening for mental illness is an imprecise proxy for identifying those with violent intent.

METZL: There’s no psychiatric diagnosis that’s aligned with harming other people, let alone shooting people. And the diagnoses that get thrown around in the aftermath of these horrible crimes like schizophrenia or depression, other factors like that, themselves are not aligned with violent attacks toward other people. And in that regard, there also are no tools that psychiatrists can use to say this one person with mental illness is going to harm somebody else, and this other person is not.

Many mental illness diagnoses are made after the shooting has occurred, and thus could not have been used as a predictive factor. Moreover, the diagnosed illnesses are not inherently indicative of intent to harm others – the vast majority of individuals with the same diagnoses are not violent.

And I guess the last reason is that, as we’re seeing after the horrible mass shooting in Florida, many mass shooters don’t meet the criteria for severe mental illness in any way that would cause them to be flagged on a background check system, let alone hospitalized in a psychiatric hospital.