Mental Illness Didn't Make Him Do It

Research challenges the supposed link between mental illness and violence.

Posted Feb 15, 2018

Source: Pixabay

It’s happened again. A gunman opened fire at a high school in Parkland, Florida, killing 17 people and gravely wounding several others. The news plays the familiar videos of teenagers proceeding out of their school single file, SWAT teams patrolling hallways and classrooms, interviews with students who survived and their parents. As images of the shooter play across our televisions and computers, the familiar question arises: “Why?” Many were quick to offer an answer: because the gunman was mentally ill.

The New York Times reported that the family with whom he was staying following the death of his mother noticed signs of depression, but nothing suggesting that he was capable of such brutality. The Washington Post ran a story on the shooter with the headline: “Florida shooting suspect Nikolas Cruz: guns, depression and a life in trouble.” This morning, the President tweeted, “So many signs that the shooter was mentally disturbed,” and encouraged anyone noticing such signs to alert the authorities. The suggestion is clear: Mental illness made him do it. But is that how it works?

The supposed link between mental illness and violence is so ingrained in our culture that stories like the above need only suggest that the perpetrator was depressed to satisfy a need for an explanation. Research reveals a far different story, however. People with mental illnesses are actually far more likely to be victims rather than perpetrators of violence (Appleby et. al., 2001). Those with severe mental illnesses (schizophrenia, bipolar disorder, psychosis) are actually 2.5 times more likely to be victims of a violent crime than the general population (Hiday, 2006). A 2011 study found that to prevent one violent homicide by a person with schizophrenia, 35,000 patients deemed to be at a high risk of violence would need to be detained (Large et. al., 2011). And yet the link persists. A 2013 survey conducted after the Newtown shooting found that 46 percent of Americans believe that persons with a serious mental illness are “far more dangerous than the general population” (Barry et. al., 2013).

The stereotype about violence and mental illness is not just inaccurate; it is dangerous. Every story that suggests a causal link between mental illness and violence further increases the stigma of having a mental illness, making it less likely that those experiencing a mental illness will seek help. This supposed link also hurts the general population, because it communicates the implicit message that mental illness is something to be feared. This further isolates those with mental illness from the surrounding community, when we know that being integrated into society increases functioning and well-being for those with a mental illness. Finally, the stereotype is just lazy; it lets us off the hook far too easily. If we can blame violence on the perpetrator’s mental illness, then we don’t have to dig back too far into his history to find the ways in which we failed to notice warning signs, or the ways in which our gun laws enable civilian access to military weapons, among other things.

Why did he do it? We don’t know. It’s all too human to wonder; our minds struggle with ambiguity. If and when we find out, it will never fully explain how someone could murder 17 of their former classmates and teachers in cold blood. We do know one thing, though: Mental illness didn’t make him do it.

In a follow up post I identify some common logical fallacies in the supposed link between mental illness and violence.


Appleby, L., Mortensen, P. B., Dunn, G., & Hiroeh, U. (2001). Death by homicide, suicide, and other unnatural causes in people with mental illness: a population-based study. The Lancet, 358, 2110-2112.

Barry, C.L., McGinty, E.E., Vernick, J.S., & Webster, D.W. (2013). After Newtown–Public opinion on gun policy and mental illness. New England Journal of Medicine, 368,1077–1081.

Hiday, V. A. (2006). Putting Community Risk in Perspective: a Look at Correlations, Causes and Controls. International Journal of Law and Psychiatry, 29, 316-331.

Large, M.M., Ryan, C.J., & Singh, S.P., et al. (2011). The predictive value of risk categorization in schizophrenia. Harvard Law Review, 19, 25–33. 

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