It’s key that the emotion is “overwhelming.” Human brains have evolved to deal effectively with mild to moderate fear stimuli—it’s only when experiencing extraordinary fear (or another emotion) that our bodies become less well-suited to cope. Humaira Siddiqi, the chief of psychiatry at Kaiser Permanente in northern Virginia, tells me that when we start to experience fear, or any other emotion, it begins in a part of the brain called the amygdala. In mild to moderate cases, this information is then relayed to the hippocampus, situated directly above it. The hippocampus puts our emotions into context. Consider your reaction any time you think you spot something moving from the corner of your eye—your amygdala may process fear or alarm, thinking you’ve seen a mouse, or a centipede, or something else awful. The hippocampus is where you realize you either saw (a) nothing, or (b) yes, a mouse or a centipede, but neither one will hurt you. Only when fear is too big and too sudden do people run into trouble. “When you have a massive surge of a fear response, it can sometimes bypass the hippocampus, and when it does that, the fear doesn't have a context,” says Siddiqi. “It's just fear. It hijacks the brain.”

When such a massive fear response occurs, the body releases a surge of hormones (epinephrine, norepinephrine, and cortisol), which can lead to an irregular heartbeat, increased blood pressure, stroke, heart attack, and as a result, death (though it’s unlikely). Part of the reason for this hormone release is what Siddiqi describes as an ultimately outdated evolutionary response to fear: fight or flight. “Our modern fear typically doesn't require a physical response. It requires us to think. So in a sense we're sort of tackling the fear stimuli with outdated adaptation from our evolution.”

Because people don’t (usually) address our fears by literally running away, or fighting, the excess adrenaline doesn’t serve their actual needs. In fact, in cases of extreme fear or anxiety, says Siddiqi, it’s usually best for people to “override” their body’s fear response by taking deep, measured breaths. “Things like taking a few deep breaths might seem kind of silly, but when you're breathing, it makes the heart slow down a little bit,” she says. “You're consciously slowing down the body’s sympathetic response, and when you do that, the grip the sympathetic system has on the body is loosened, and you're allowed now to relax and get [in] control.”

Dying of fear (or any strong emotion) is very unlikely, though the risk increases somewhat with advancing age and the development of any underlying heart condition, says Steinbaum. And fear is not our enemy, but our ally.

“It's a good thing that we have the fear response. It's a good thing that we have anxiety, and it's even a good thing we have depression, because they are signals or alarms that something's wrong,” says Siddiqi. Fear is helpful to survival much, much more often than it is a threat. “We've evolved with fear as an adaptive mechanism,” she says. “If something like that could kill us off, we would not have evolved with it.”

All that said, it’s always worthwhile to understand and honor one’s personal threshold. There is a reason for those signs outside roller coasters warning people with heart conditions not to ride. There is a reason some people cannot and will not be talked into seeing It, even if I assure them it’s not that scary. There is a reason I will never in a million years ever jump out of an airplane hoping my parachute opens. Fear probably won’t kill you, but then again, why risk it?

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