As security heightens, so does your heart rate. (EPA/STEPHANIE LECOCQ)

As recent attacks in Paris, MaliColorado Springs and San Bernardino show, threats of terrorism and mass violence are all too real. But could your fear of such attacks be more deadly than the unlikely chance you will be physically hurt by terror? Recent research suggests the answer could be yes.

Israeli neuroscientist Shani Shenhar-Tsarfaty, who lives in Jerusalem, became interested in the psychological and physical effects of fear through both her work and daily life. “I’m very interested in vulnerability to fear,” she says. She got a chance to study just that while analyzing a large dataset from the Tel Aviv Medical Center Inflammation Survey.

The survey, which follows 17,380 apparently healthy workers over time, includes a substantial questionnaire that asks participants to quantify their fear of terror — including worries about personal safety, heightened tension while in crowded places and fear of a terror strike harming them or their families. Shenhar-Tsarfaty wondered if those emotions might be linked to certain biomarkers linked to morbidity and mortality.

Blood pressure and pulse have long been considered predictors of not only cardiovascular health but of heightened risk of death from stroke, heart attack and congestive heart failure. Since pulse rates tend to decrease over time, increases can indicate serious heart issues. In other research, for example, participants whose resting heart rate rose by 15 beats per minute were 90 percent more likely to die during the study.

Researchers aren’t yet sure of a complete list of factors that cause pulse rates to rise over time. Shenhar-Tsarfaty questioned whether fear of terror could be implicated in that and elevated levels of C-reactive protein, a biomarker that increases in response to inflammation and signals risk for conditions like cancer and heart disease. And when she and her team compared answers to questions about fear of terror to heart rate measurements over time, they found “major contributions to annual pulse increases and effects of inflammation”—despite the fact that nobody surveyed was present at the time of a terror attack. 

Shenhar-Tsarfaty is quick to point out that correlation is not causation. “We didn’t prove causality,” she insists. But high fear of terror predicted higher pulse rates in 4.1 percent of the cohort. C-reactive protein markers were higher, too.

“I can’t tell you whether fear of terror will make you die,” she says. But she believes there’s definitely a link—one that she connects to the ongoing stress of terrorism. She points out that residents of Tel Aviv have been subject to violence, war and chaos for over 60 years. She's now digging deeper into what genetic and physical factors could influence individual responses to ongoing threats. In the future, she hopes this research can be used to inform public response to terror and help individuals become more aware of their degree of fear and its stressful impact on health. 

Though her work took place in Israel, Shenhar-Tsarfaty’s study could be relevant in any place that is grappling with real or perceived threats of terror. If 4.1 percent of Americans were to experience potentially fatal cardiovascular events from their fear of terror, their risk of death would be much greater than the likelihood that they could die in a terrorist attack.

Maybe “fear of terror” belongs on the long list of things more likely to kill you than terror itself.

Erin Blakemore (@heroinebook) is a freelance journalist from Boulder, Colo. She is the author of The Heroine’s Bookshelf (Harper). 

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