A new study provides evidence that unaddressed mental health issues might increase violence in mass shootings. The findings have be published in the journal Psychology, Public Policy, and Law.

“I became interested in this topic for reasons probably similar to other researchers who have become interested in mass shootings. Initially, I was interested in why they occurred, but as I read more, I became more interested in how they differed,” said Logan A. Yelderman, an assistant professor of psychology at Prairie View A&M University and the corresponding author of the study.

“Much of the discussion about mass shootings surrounded how to prevent them, distinguishing between who is likely to become a shooter and who is not. I think that is the ultimate question people want answered, but I became more and more interested in how each mass shooting differed and what factors might have contributed to these variations.”

“I asked myself the simple question, ‘are the factors associated with variations in violence across shootings similar to those which predict them?’ I also wanted to know if certain policies might be helpful in addressing these factors. Thus, this research began.”

Yelderman and his colleagues analyzed 102 cases of mass shooters in the United States between 1982 and 2018. They found that most shooters obtained their guns legally (82.4%) and mental illness was reported to some extent in slightly over half of the cases (54.9%). About one-fourth of the mass shooters had spent time in a mental health facility or program. The average number of victims was 22.

The researchers found that mass shooters in which a mental disorder had been mentioned but no formal diagnosis was reported tended to have the most victims, compared to those with no reported mental health history and those who had received a formal diagnosis.

The Pulse nightclub shooter, for instance, was described as bipolar and mentally unstable by his wife, but had not been diagnosed with any specific condition. He killed 49 people and wounded 53 others.

“Our findings suggest that mass shooters with suspected mental health issues, yet who lacked formal diagnosis, tended to be more violent. This potentially implies that formal contact with mental health professionals or formal awareness of mental health might provide some buffering effect on violence among mass shooters. Also, shooters who had access to more weapons during the shooting tended to be more violent,” Yelderman told PsyPost.

“The main take-away (specific to policy) from our research is that policy discussions about mass shooting violence should not center on only guns or mental health but instead on gun ownership and responsibility and mental health. Two separate policies, one being a gun ban and the other being a mental health history restriction, are not the same as an integrative policy incorporating both mental health and gun control,” he added.

“Essentially, both mental health and firearm ownership/responsibility are key factors associated with mass shooting violence, and both need to be integrated in policy development and implementation. To focus on one and neglect the other would be unwise.

But the study — like all research — includes some limitations.

“There are three main caveats. First, our research addresses variations in violence among mass shooters; it does not address what leads people to become mass shooters,” Yelderman explained.

“Second, our data come from media and police reports; we did not have clinicians evaluate or validate diagnoses among the mass shooters, primarily because this proved problematic as most were deceased as the result of suicide or being shot by law enforcement. Nevertheless, we were unable to verify the reports independently.”

“Third, there are numerous ways to define a mass shooting, and we chose a definition that we thought represented the most accurate depiction of what current policy debates are actually about; however, it is possible that using other definitions might reveal different patterns in mass shooting violence.”

The study focused on seemingly random public shootings that resulted in more than three or four deaths. The researchers did not examine mass shootings related to gang activity and family slayings.

“Though policy is typically a good tool to improve the welfare of Americans, sometimes improvement requires change at the individual and community levels. Regarding mass shootings and other firearm violence, policy debates must include discussions about fundamental change in culture surrounding guns and mental health; otherwise, it is possible that policies will continue to risk failure,” Yelderman added.

“Developing policy to address gun violence should not be based on mass shootings alone, as they make up for a very small percentage of gun violence. Instead these policies should consider firearm violence of all kinds, including both mass shootings and non-mass shootings.”

The study, “Mass Shootings in the United States: Understanding the Importance of Mental Health and Firearm Considerations“, was authored by Logan A. Yelderman, Justin J. Joseph, Matthew P. West,and Erycha Butler.