Your Heart Races, But You're Not Anxious. Here's Why.

COMT (catechol-O-methyltransferase) is the enzyme responsible for breaking down and clearing your stress hormones: dopamine, norepinephrine, and epinephrine. When COMT is working at normal speed, stress hormones spike in response to a threat and then clear rapidly once the threat is gone. Your nervous system returns to baseline. Your heart rate slows. You feel calm again.

Here’s the problem: if you carry the Val158Met variant on the COMT gene, you may have a slower version of this enzyme. Roughly 25% of people with European ancestry are homozygous for the slow variant. Your stress hormones can remain elevated for hours after a stressor has passed, even though nothing is actively threatening you. Your body keeps the alarm running long after the fire is out.

What this feels like in your body: your heart won’t slow down even after the stressor is gone. You feel jittery or shaky hours after a tense conversation or a mild frustration. You’re sensitive to stimulation (noise, crowds, bright lights) because your baseline dopamine and norepinephrine are already elevated. Your hands tremble. You feel wired, even when you should be tired.

FKBP5 (FK506 binding protein 5) is part of your HPA axis feedback loop, the system that tells your adrenal glands to stop producing cortisol when stress has passed. It works by making your cortisol receptors more sensitive, so a small amount of cortisol triggers a strong signal: “You can relax now.” When FKBP5 is working well, your cortisol spikes briefly during stress and then drops.

If you carry the rs1360780 variant of FKBP5, roughly 30% of people do, your cortisol receptors become less responsive. Your body doesn’t get the memo to turn off cortisol production, so it stays elevated long after the stressor is gone. Your HPA axis is like a car without a good brake. The accelerator works fine, but stopping takes a long time.

What this feels like: your body stays in fight-or-flight mode for hours or even days after a mild stressor. You wake up with your heart racing even though nothing happened overnight. You feel a persistent undercurrent of threat in your body, even on calm days. Your chest tightness doesn’t come and go; it lives there.

SLC6A4 codes for the serotonin transporter, the protein that recycles serotonin back into neurons after it’s been released. This recycling is how your brain maintains stable serotonin levels throughout the day. When serotonin recycling is efficient, you have a steady buffer against stress. When it’s slow, serotonin becomes depleted under pressure.

If you carry the short allele of the 5-HTTLPR polymorphism in SLC6A4, roughly 40% of people carry at least one short allele, your neurons recycle serotonin less efficiently. Under stress or sensory stimulation, your available serotonin drops rapidly, and your amygdala (your brain’s alarm system) becomes hyperactive. You lose your emotional and sensory shock absorber.

What this feels like: your body responds to minor stressors as if they were major threats. A conversation with your boss triggers the same heart racing and trembling as a car almost hitting you. Crowded places feel genuinely overwhelming. You’re not overreacting; your serotonin buffer is depleted, and your threat detection system is running hot.

MAOA (monoamine oxidase A) is the enzyme that breaks down and clears serotonin, dopamine, and norepinephrine from your synapses. It’s your brain’s cleanup crew. When MAOA is working efficiently, neurotransmitters are cleared at a steady, predictable rate. Your nervous system stays balanced.

If you carry the MAOA-L (low-activity) variant, roughly 30-40% of males carry this variant, your cleanup crew works more slowly. Your neurotransmitters accumulate in your synapses, creating unpredictable spikes and fluctuations in dopamine and norepinephrine. Your nervous system experiences waves of activation that don’t match your circumstances. You’re calm one moment and your heart is pounding the next.

What this feels like: your physical anxiety symptoms come in waves that seem disconnected from anything you’re doing. You might feel a sudden surge of heart racing, trembling, or chest tightness without any trigger. You feel reactive and unpredictable to your own body. You might also have a low tolerance for alcohol or certain medications because your neurotransmitter levels spike higher and linger longer.

BDNF (brain-derived neurotrophic factor) is a protein that helps your brain adapt to stress and recover from it. It’s like the repair crew for your nervous system. When stress hits, BDNF increases neuroplasticity, the ability of your brain to rewire itself and adjust. It also supports growth of new neurons and strengthens your prefrontal cortex, which is your brain’s rational, calm part.

If you carry the Met allele of the Val66Met variant in BDNF, roughly 30% of people carry at least one Met allele, you produce less BDNF in response to stress. Your brain struggles to adapt when pressure builds, and your prefrontal cortex becomes less able to regulate your amygdala and brainstem threat response. Each stressor leaves you more depleted, not stronger.

What this feels like: your physical anxiety symptoms don’t improve with exposure or coping strategies. You don’t “get used to” situations that stress you. Instead, repeated stress seems to make your nervous system more reactive and fragile. You recover more slowly from stressors. You feel like your nervous system is getting worse, not better.

NR3C1 codes for the glucocorticoid receptor, the protein that allows your cells to respond to cortisol. Cortisol is often called a “stress hormone,” but it actually serves a critical calming function: it tells your body “the threat has been addressed; you can recover now.” It dampens inflammation and immune activation and shifts your body from fight-or-flight back to rest-and-digest. When glucocorticoid receptors are working well, cortisol delivers this calming signal efficiently.

If you carry variants in NR3C1, roughly 30% of people carry relevant variants, your glucocorticoid receptors may be less sensitive or less available. Even though your cortisol levels might be normal or even high, your cells aren’t receiving the calming signal well. Your body keeps the stress response activated because the brake pedal isn’t connecting to the engine.

What this feels like: your body stays in a low-grade fight-or-flight state even when nothing is happening. You feel chronically “on alert.” Your heart races easily. You startle easily. You have trouble sleeping even when you’re exhausted. Cortisol-lowering strategies (like relaxation) help temporarily, but the underlying responsiveness remains because the problem is at the receptor level, not the hormone level.