New research provides evidence that religious prejudice can influence how people perceive mass shooters. The study, published in the journal Psychology of Violence, found that people prejudiced against Muslims tended to view Muslim mass shooters as less mentally ill compared to non-Muslim shooters.

“While mass shootings makeup only a small percentage of total gun deaths, they are an issue that many members of the public are extremely concerned about,” said study author Brett Mercier of the University of California Irvine.

“As mass shootings in the United States are almost certain to continue, I think it is increasingly important to understand how the public responds to them. Up until now, there hasn’t been that much research on this topic. For this particular paper, my co-authors and I noticed that there appeared to be a double standard in how many people treated shooters who are Muslim, relative to shooters who are not.”

The study, which included more than 2,600 participants, found that Muslim mass shooters tended to be viewed as less mentally ill and more motivated by religion — but only among those with negative views toward Muslims.

“Our research finds that individuals who have negative attitudes towards Muslims discount mental illness for mass shooters who are Muslim. This means that those with negative views of Muslims are probably overestimating how much violence is caused by extremist Islamic groups,” Mercier told PsyPost.

The researchers also found that participants with negative attitudes toward Muslims viewed Muslim shooters as less mentally ill than Christian mass shooters. They also viewed Muslim shooters as less mentally ill even they were described as having symptoms of mental illness.

“Selectively discounting the role of mental illness for members of some ideologies but not others may create inaccurate estimations of the degree and frequency in which those ideologies inspire violence. We do not claim that groups like ISIS or al-Qaeda never play a role in inspiring mass shootings (they do) or that violence from these groups and their local acolytes is not a threat (it is),” Mercier and his colleagues wrote in their study.

“However, if violence committed by Muslims is reflexively viewed as ideologically motivated terrorism, whereas violence committed by members of other groups is attributed to mental illness, people risk having an imbalanced view of these threats — overestimating the threat posed by extremists who are Muslim relative to the threat posed by extremists from other ideologies.”

Surprisingly, there was no evidence that people used mental illness to exonerate mass shooters belonging to their own religious group. Christian participants were not more likely to view Christian mass shooters as more mentally ill, nor were Muslim participants more likely to view Muslim mass shooters as more mentally ill.

“Although mass shooters are often mentally ill, it is important to remember that mass shooters make up a very small percentage of individuals who are mentally ill,” Mercier noted. “The vast majority of individuals with mental illness are not violent, and there is no reason to be afraid of persons with mental illness,”

The study, “Muslim Mass Shooters Are Perceived as Less Mentally Ill and More Motivated by Religion,” was authored by Brett Mercier, Adam Norris, and Azim F. Shariff.