Fear is one of the body’s most essential survival mechanisms. An instinct that has helped humans and other animals avoid danger and stay alive for a long time. Yet for a small number of people, this primal emotion is absent altogether. Studying these rare individuals offers remarkable insight into how fear is generated, regulated, and expressed in the brain – and what happens when those systems fail.
When Fear Disappears
For most of us, fear triggers are easy to identify – heights, enclosed spaces, or public speaking. But for British patient Jordy Cernik, fear became a complete stranger after he underwent surgery to remove his adrenal glands. The procedure, intended to treat Cushing’s syndrome (a rare endocrine disorder caused by excess cortisol), successfully reduced his anxiety but also erased his ability to feel fear.
After surgery, Jordy could jump from a plane, abseil down London’s Shard, or zip-line off the Tyne Bridge – all without the usual surge of adrenaline or elevated heart rate. His case highlights how deeply intertwined our hormones and neurochemistry are in regulating emotional responses.
The Amygdala and the Architecture of Fear
While Jordy’s experience is extraordinary, a handful of even rarer cases have provided deeper insights into the neurobiology of fear. Among them is a patient known simply as “SM” who has been studied for decades by neuroscientists at the University of Iowa. SM lives with Urbach-Wiethe disease, a genetic disorder caused by mutations in the ECM1 gene, which leads to calcification and damage in parts of the brain, including the amygdala.
The amygdala is central to fear processing. In SM’s case, bilateral damage to this region erased her ability to experience fear from external threats. Horror films, snakes, and haunted houses all left her unmoved. In fact, researchers observed an unusual curiosity, she would approach rather than avoid frightening stimuli.
The Dual Pathways of Fear
However, the story of fear is not limited to the amygdala. In one experiment, SM and two other patients with amygdala damage were asked to inhale air enriched with carbon dioxide, triggering the sensation of suffocation. To researchers’ surprise, all three experienced intense panic attacks, the first time SM had felt fear in her adult life.
This discovery revealed two distinct fear pathways in the brain:
- External threat processing, coordinated by the amygdala, which governs responses to visible or environmental dangers such as predators or threats from others.
- Internal threat detection, mediated by the brainstem, which monitors internal bodily states such as oxygen and carbon dioxide levels. When CO₂ rises, the brain interprets this as suffocation, inducing panic – even without amygdala input.
This distinction challenges long-held assumptions that the amygdala is the sole seat of fear. Instead, it acts as a conductor for external danger signals, while internal threats rely on more primitive brain circuits.
The Role of Fear in Survival and Society
From an evolutionary standpoint, fear has been critical for survival. Damage to the amygdala in animal studies results in rapid mortality, as affected animals lose the instinct to avoid predators and other dangers.
In humans, however, the relationship between fear and wellbeing is more nuanced. While the absence of fear can expose individuals to risk, excessive or chronic fear contributes to anxiety, stress disorders, and impaired quality of life. As Dr Justin Feinstein, a neuropsychologist involved in SM’s research, has observed, “Fear may not be as necessary in modern life as it once was. In societies where basic safety is largely assured, chronic fear responses can do more harm than good.”
Rethinking Fear in Healthcare
Understanding the neurobiology of fear has practical implications across medicine and mental health. It informs new approaches to treating anxiety, phobias, and PTSD, as well as guiding research into neuroendocrine disorders like Cushing’s syndrome that affect emotional regulation.
These cases remind us that fear, while sometimes distressing, remains a finely tuned biological signal, essential for both personal safety and adaptive functioning. In today’s world, the challenge for clinicians and researchers is not eliminating fear, but understanding how to balance it: reducing maladaptive anxiety while preserving this ancient instinct’s protective power.
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