Here we are again. The recent terrorist attack in El Paso has revived an ongoing debate: When do attacks get covered as terrorism and when are they attributed to mental illness?

Our research previously found that attacks perpetrated by a Muslim receive 357 percent more coverage on average than those committed by non-Muslims or unknown perpetrators.

Before the shooting of dozens at a Walmart and shopping center in El Paso, a manifesto was posted online filled with anti-immigrant sentiment. Given its white supremacist language and its expressed intention to make Latinos fear the United States, law enforcement, media and experts alike quickly began calling this a terrorist attack. At the same time, some politicians and media coverage still raised questions about the attacker’s mental health. Most prominently, President Trump gave a speech decrying the shootings in both El Paso and Dayton, Ohio, by saying that “mental illness and hatred pulls the trigger, not the gun.”

Our recent study finds that, indeed, news articles are drastically more likely to call an attack terrorism when the perpetrator is Muslim. But whether the perpetrator is white does not influence whether the news coverage will suggest mental illness. We explain below.

How we conducted our research

A number of observers have suggested that the news media call Muslim perpetrators “terrorists” while white perpetrators are described as “mentally ill.” Political scientists Bryan Arva, Muhammed Idris and Fouad Pervez found that to be true when they compared news coverage of four high-profile attacks, two perpetrated by Islamist extremists and two by white supremacists. To see whether that contrast held up more generally, we undertook a systematic evaluation of all such attacks rather than just a subset of them.

Here’s how we identified cases and collected media coverage of them. We first identified all terrorist attacks, as listed in the Global Terrorism Database, that occurred in the United States from 2006 through 2015. In the GTD, terrorism is defined as “the threatened or actual use of illegal force and violence by a nonstate actor to attain a political, economic, religious, or social goal through fear, coercion, or intimidation.”

During the 10-year period we studied, there were 136 attacks in the United States. We collected U.S.-based print media coverage of these attacks from and LexisNexis Academic, which pulls from 15,000 news sources across the world, including major outlets like The Washington Post as well as local newspapers around the United States. More partisan sources like Fox News and HuffPost do not have searchable archives, so we could not include them in the study. We included only articles that primarily focused on the attack, the perpetrator(s) or the victims, finding 3,541 articles that met the criteria. Thirty-six of the attacks did not receive coverage from these sources, so we focus on articles for 100 attacks in total.

We next identified whether each article refers to terrorism or mental illness, using the qualitative data analysis software Nvivo, searching for key terms relating to terrorism and to mental illness. We then compared references to terrorism for Muslim vs. non-Muslim perpetrators and references to mental illness for white vs. nonwhite perpetrators.

When a perpetrator is Muslim, there’s a 488 percent greater chance an attack will be called terrorism

Only 17 percent of the attacks we studied were perpetrated by Muslims — but of the 1,384 articles that mentioned terrorism, 77 percent were covering these attacks. Of course, other factors had an effect; if an attack was perpetrated by members of an identified terrorist group, then coverage was understandably more likely to mention terrorism. And when the perpetrator was known or suspected of having a mental illness, media coverage was less likely to refer to terrorism.

Even controlling for these factors, we found that the odds of an article using the term “terrorism” is 488 percent greater when the perpetrator is Muslim.

But when an attacker is white, it doesn't increase the chance that media coverage will mention mental illness

To our surprise, we found no differences in references to mental illness based on whether the perpetrator was white. Rather, when the perpetrator was known to have or suspected of having a mental health issue, coverage was understandably more likely to mention mental illness. But when an attack included several perpetrators or when the perpetrator was associated with a known white supremacist or other terrorist group, mental illness was much less likely to be mentioned.

Why does this matter?

Whether intentional or not, by associating terrorism and Islam, the news media distorts public perceptions of threats and misleads the public about who perpetrates terrorism. While some perpetrators of terrorist attacks might be correctly characterized as mentally ill, this is largely atypical. The American Psychological Association finds no link between mental illness and perpetrating violence. The idea that many mass shootings are committed by those who are mentally ill is unsubstantiated.

No matter what the news media may intend, these disparities in coverage are stark. By overwhelmingly framing attacks by Muslims as terrorism — and emphasizing that designation far more than about similar attacks by non-Muslims — the news media both perpetuates misconceptions about terrorism and suspicion of Muslims. That coverage can influence public opinion and policy.

Perhaps the explicit designation of domestic, white nationalist terrorism in the El Paso shooting, which many news outlets are linking to similar attacks over the past several years, will begin to change this.

Allison Betus (@AllisonBetus) is a PhD candidate in the department of communication and Craigie International Security Scholar in the Global Studies Institute at Georgia State University.

Erin M. Kearns (@KearnsErinM) is an assistant professor of criminology & criminal justice at the University of Alabama and the corresponding author for this study.

Anthony Lemieux (@aflemieux) is the director of the Global Studies Institute, co-director of the Atlanta Global Studies Center, and a professor of global studies and communication at Georgia State University.