Franklin D. Roosevelt no doubt meant to be soothing when he insisted, “The only thing we have to fear is fear itself.” A quick and terrifying tour through the academic literature on fear, though, reveals just how much heavy lifting that only was doing.
Our fears run broad and deep, and are every bit as diverse as we are. The 2017 version of Chapman University’s Survey of American Fears tabbed “corruption of government officials” as the most common fear, afflicting nearly 75 percent of respondents; concerns about the health-care system, the environment, personal finance, and war also figured in the top 10. Such spine-tingling triggers as public speaking and enclosed spaces landed in the bottom half of the 80 fears polled; clowns were slightly more scary than zombies, who were only slightly more scary than ghosts.
One reason we struggle with fear is that we’re simultaneously too primitive and too evolved for our own good. Our lizard brains are ruthlessly efficient: Signals speed to the threat-sensing amygdala within 74 milliseconds of the slightest hint of danger.  This speed has, over eons, helped save us from extinction. But it’s also led to plenty of false alarms.
Part of the problem is that our forebears’ oldest fears are still with us. Even babies exhibit a fight-or-flight response to pictures of snakes and spiders, presumably as a result of instinct rather than experience.  Deep-seated aversions like these are strong enough to distort our sense of reality: People with arachnophobia are likely to overestimate the size of spiders relative to other organisms.  Such ancestral sensitivities may also account for trypophobia, the fear of closely clustered circles (such as pores in sponges or bubbles in coffee)—which, according to one study, may affect up to 16 percent of the population. Research by two groups of psychologists in the U.K. proposes that small circles’ resemblance to parasites and to distinctive patterns on poisonous animals may be enough to trigger this atavistic response. [4, 5]
Our higher consciousness is supposed to help us sort out these threats, but at times it seems more committed to spinning out anxious what-ifs about imperiled loved ones and unattended stoves. An entire body of risk-perception research has detailed just how bad we are at figuring out which dangers are worth worrying about. We tend to overestimate the threat of dying by lightning, flood, or murder, while underestimating the much more immediate threats posed by asthma, stroke, and diabetes, among other unsexy hazards. 
In the wake of 9/11, airplane ridership plummeted in the United States as many people opted to travel by car. A German psychologist estimated that in the 12 months following the attacks, 1,595 more people were killed in car accidents than would be expected in an ordinary year.  That’s more than six times the number of passengers (246) who died on the four hijacked airplanes. At its worst, then, fear can backfire, bringing about the very outcome we were afraid of in the first place.
So in the end, we have to face an undeniable but discomfiting fact: The only thing we have to fear is corruption, clowns, diabetes, tiny coffee bubbles, unintended consequences … and fear itself.
 Méndez-Bértolo et al., “A Fast Pathway for Fear in Human Amygdala” (Nature Neuroscience, Aug. 2016)
 Hoehl et al., “Itsy Bitsy Spider …” (Frontiers in Psychology, Oct. 2017)
 Leibovich et al., “Itsy Bitsy Spider?” (Biological Psychology, Dec. 2016)
 Cole and Wilkins, “Fear of Holes” (Psychological Science, Oct. 2013)
 Kupfer and Le, “Disgusting Clusters” (Cognition and Emotion, July 2017)
 Hertwig et al., “Judgments of Risk Frequencies” (Journal of Experimental Psychology, July 2005)
 Gigerenzer, “Out of the Frying Pan and Into the Fire” (Risk Analysis, April 2006)
This article appears in the June 2018 print edition with the headline “What Are You Afraid of?”