You're Sensitive to Everything. Here's the Biological Reason.

COMT is an enzyme that breaks down dopamine, norepinephrine, and epinephrine in your prefrontal cortex. This is the part of your brain responsible for decision-making, emotional regulation, and filtering out irrelevant sensory information. When COMT is working normally, it clears these neurotransmitters at a steady rate, keeping your mind calm and focused.

The Val158Met variant of COMT determines how fast this enzyme works. The slow version (Met/Met), carried by roughly 25% of people with European ancestry, produces an enzyme that clears dopamine much more slowly than normal. This means dopamine accumulates in your prefrontal cortex, raising your baseline arousal level. Your brain is essentially running in a state of constant mild overstimulation, with too much dopamine and stress hormone circulating at any given time. Your nervous system is stuck in a higher gear.

This manifests as hypersensitivity to sensory input. A normal volume feels loud. A normal-bright room feels glaring. A crowded room doesn’t just feel busy; it feels chaotic and threatening. Your stress response doesn’t turn off quickly because your stress hormones aren’t being cleared fast enough. You feel wired after social events, keyed up after work, and unable to relax even when there’s nothing to do.

SLC6A4 encodes the serotonin transporter, a protein that pulls serotonin out of the space between nerve cells so it can be reused. Serotonin is your brain’s primary mood and emotional stability neurotransmitter. It also buffers your emotional response to sensory input. When serotonin recycling is working well, minor annoyances don’t feel like catastrophes, and social interactions don’t deplete you.

The 5-HTTLPR short allele variant, carried by roughly 40% of the population, reduces the efficiency of the serotonin transporter. This means serotonin doesn’t get recycled as quickly, and more of it is broken down instead of reused. Your available serotonin drops faster under stress, leaving you emotionally reactive and hypersensitive to social and environmental stimuli. You have less emotional buffer. The world feels more intense, more threatening, and more tiring.

You probably notice this as emotional exhaustion after social situations. One difficult conversation leaves you emotionally drained for hours. A mildly rude interaction replays in your head all day. You feel things more intensely than other people seem to. You’re more reactive to criticism, more bothered by social rejection, and quicker to feel anxiety in uncertain situations. Your nervous system is hypersensitive to the emotional content of your environment.

MTHFR encodes methylenetetrahydrofolate reductase, an enzyme that converts folate into its active form, methylfolate. This active form is essential for producing neurotransmitters, regulating inflammation, and supporting nerve cell function. Without efficient MTHFR activity, your neurons don’t have the chemical building blocks they need to function properly.

The C677T variant, carried by roughly 35-40% of people, reduces this enzyme’s efficiency by 40-70%. The A1298C variant has a milder effect. Both impair your ability to convert dietary folate into the active form your brain needs. You can eat a perfect diet rich in folate and still be functionally depleted at the cellular level because your cells can’t process what you’re eating. Your neurotransmitter production suffers. Your inflammatory regulation suffers. Your nerve cell protection suffers.

This shows up as heightened sensory sensitivity, brain fog, mood instability, and slower recovery from stress. Your nervous system is running on incomplete fuel. You feel more scattered than you should be. You’re more reactive to stress. You fatigue more easily. You might have chronic tension headaches or muscle tension that seems disproportionate to your stress level.

BDNF is brain-derived neurotrophic factor, a protein that helps your nervous system adapt to stress and form new neural connections. It’s essential for learning, memory, and recovery from emotional or physical stress. A healthy BDNF system means your brain bounces back from difficult experiences and doesn’t stay stuck in a heightened stress state.

The Val66Met variant, carried by roughly 30% of people, reduces BDNF production. This particularly affects your ability to recover from stress. Your nervous system gets activated by sensory or emotional threats, but it doesn’t reset as quickly afterward. You stay in a state of mild alarm longer than other people. Each stressful experience makes it harder to bounce back. Over weeks and months, this accumulated stress burden leaves you increasingly hypersensitive.

You probably notice this as progressively worsening sensitivity. You’re okay for a while, handling sensory input reasonably well. But after repeated stress or overstimulation, you hit a wall. Your tolerance drops. Everything becomes irritating. You feel more fragile. This isn’t character weakness. It’s your nervous system lacking the biochemical tools to rebuild itself after stress.

ADORA2A encodes the adenosine A2A receptor, a protein on nerve cells that responds to adenosine, a chemical that builds up during wakefulness and signals your brain to rest. This is how your body creates sleep pressure. When you’re awake, adenosine accumulates. When adenosine hits the A2A receptor, your brain gets the signal that it’s time to slow down. Caffeine works by blocking these receptors.

The C/C variant of rs5751876, found in roughly 10-15% of the population, creates a hyperactive adenosine receptor. This means your brain is extra responsive to adenosine and extra sensitive to caffeine. Your nervous system is wired to react more strongly to any stimulant, and it produces stronger sleep pressure than average. You’re naturally more sensitive to caffeine’s effects. But you’re also more sensitive to any stimulating input: loud noises, bright lights, fast-paced activity, or overstimulating social situations all feel more intense.

You probably notice this as an inability to tolerate caffeine like other people do. Even small amounts make you jittery. You’re sensitive to overstimulation in general. You might be a naturally light sleeper or easily awakened by noise or light. Your nervous system has a lower threshold for stimulation overall.

FKBP5 encodes a protein that regulates glucocorticoid receptors, the cells’ main mechanism for shutting off the stress response. When cortisol binds to these receptors, it tells your body the threat has passed and it’s time to calm down. A healthy FKBP5 system means your stress response turns off quickly and efficiently. When something startles you, your heart rate returns to normal within minutes. Cortisol returns to baseline. Your nervous system resets.

The rs1360780 variant, carried by roughly 30% of the population, impairs this feedback loop. Your glucocorticoid receptors become less sensitive to cortisol’s shutdown signal. This means once your stress response is activated, cortisol stays elevated longer, even after the stressor is gone. Your nervous system stays in high alert. A minor trigger that would normally resolve in minutes or hours keeps you activated for hours or days. Cortisol doesn’t drop when it should.

This shows up as heightened anxiety, prolonged sensory sensitivity after stressful events, and difficulty recovering from emotional overwhelm. You’re easily triggered. Once triggered, you stay triggered. Your nervous system is slow to recognize that the threat has passed. You replay stressful conversations, stay worried about minor problems, and have difficulty shifting your attention away from potential threats.