“A sick, demented man.” That was Donald Trump’s assessment of Stephen Paddock, who shot nearly 600 people, leaving 58 dead, during a concert in Las Vegas earlier this month. Echoing Trump’s rhetoric, House Speaker Paul Ryan said that “one of the things we’ve learned from these shootings is often underneath this is a diagnosis of mental illness.”

Most Americans think that there is a strong link between mental illness and mass shooting, and shifting the national conversation to mental health reform carries the advantage of avoiding the more politically divisive gun-control debate. But what if Stephen Paddock had no diagnosable mental illness? And what if his mental state was the rule, not the exception?

In the aftermath of a mass shooting, we naturally seek to understand the killer’s motives. Our first instinct is to assume that the killer must be mentally deranged somehow. He must be a sadist who takes pleasure in the suffering of innocents, or a psychopath who feels no empathy for his victims, or a schizophrenic haunted by paranoid delusions. How else could someone commit such an awful atrocity?

Research over the last 30 years has consistently shown that diagnosable mental illness does not underlie most gun violence.

Yet, there is no evidence that Stephen Paddock was any of those things. He had no history of mental illness. He had no criminal record. He was a successful businessman. Relatives and people who know him are in disbelief. Paddock’s father was a notorious bank robber, but the two men never met, and if Paddock inherited violent tendencies from his father genetically, they never manifested until now.

We may never know what motivated Paddock or whether he had a mental illness. However, if we expand out from this specific incident and consider gun violence as a whole, research over the last 30 years has consistently shown that Mr. Ryan’s information is incorrect and that diagnosable mental illness does not underlie most gun violence.

In their 2016 edited book Gun Violence and Mental Illness, psychiatrists Liza Gold and Robert Simon summarize the evidence debunking the myth that mental illness is a leading cause of gun violence. As they report, less than 5% of shootings are committed by people with a diagnosable mental illness. Like mentally healthy offenders, the mentally ill are far more likely to shoot people they know rather than strangers. The mentally ill are also far more likely to be victims of gun violence rather than perpetrators. These data suggest that the link between mental illness and mass shooting exists in our minds, not in reality.

This makes sense if we step back and think about it. Only four percent of the population will be diagnosed with a severe mental illness. Only one percent of the population is psychopathic, and only one percent of the population is schizophrenic, and sadism is so rare there is no agreed upon psychiatric diagnosis for it. As Gold and Simon report, the vast majority of people with these mental illnesses will not perpetrate gun violence. Therefore, even if the small fraction of the already small fraction of people diagnosed with mental illness were more likely to commit gun violence, they would not be able to account for most gun violence because of their low numbers.

Perpetuating the myth that mental illness is the cause of mass shootings only serves to stigmatize the mentally ill even further. In addition, it distracts from the more difficult conversation that must be had over gun-control in America.

Still, it can be difficult to accept that only five percent of shooting deaths are attributable to diagnosable mental illness because it feels like someone would have to be ‘crazy’ in order to shoot 600 strangers at a country music concert from a pair of hotel windows. But even if you believe that someone must be mentally ill in order to perpetrate a mass shooting, the key question is in whether that mental illness is diagnosable prior to the violent act. Remember, Paddock had no history of mental illness and no criminal record. This was not a question of adequate access to mental healthcare either. Paddock was successful and had the means to access care if he chose to. Thus, even if the most comprehensive and strictest mental health reforms were put in place, Paddock would have been unaffected; 95 percent of shooters would be unaffected.

Believing that mental illness causes mass shootings can feel reassuring. It helps to believe that only a mentally ill person could do something so horrific. We also think that if someone is mentally ill, they can be identified. But the evidence suggests that mental illness only causes a small fraction of gun violence. And even if some shooters have undiagnosed mental illness, there is no evidence to suggest that they could have been diagnosed prior to their gun violence or that such a diagnosis would increase the predictive validity of a diagnosis on gun violence.

Perpetuating the myth that mental illness is the cause of mass shootings only serves to stigmatize the mentally ill even further. In addition, it distracts from the more difficult conversation that must be had over gun-control in America.