You're doing everything right and still feel low. Here's the biological reason.

COMT’s job is to clear dopamine, norepinephrine, and epinephrine (adrenaline) from your prefrontal cortex and nervous system. Think of it as your brain’s stress hormone recycling system. It works constantly, keeping your stress chemistry in balance so you can think clearly and stay calm under pressure.

Here’s the problem: the Val158Met variant creates two versions of the COMT enzyme, slow and fast. About 25% of people of European ancestry are homozygous slow, meaning both copies of your gene encode slow clearance. When you’re a slow COMT, your stress hormones accumulate instead of being cleared, keeping you in a constant state of low-grade fight-or-flight activation. Your nervous system never fully relaxes.

What this feels like: You’re anxious for no clear reason. Small stressors feel huge. Your mood is reactive; criticism lands harder than it should. You ruminate. You can’t quite turn off your mind. Caffeine makes you feel worse, not better, because you already have too much adrenergic tone. You feel emotionally raw.

SLC6A4 encodes the serotonin transporter, a protein that sits in the cell membrane and recycles serotonin back into the neuron after it’s been released. This recycling is how your nervous system resets serotonin signaling and prepares for the next signal. Without efficient recycling, serotonin floods the synapse, then disappears; your signaling becomes erratic.

The 5-HTTLPR short allele is a structural variant that reduces the transporter’s expression and function. Roughly 40% of people carry at least one short allele. If you have one or two short alleles, your serotonin recycling is impaired, causing serotonin to linger in the synapse longer than it should, then crash. This creates a seesaw effect: overstimulation followed by depletion.

What this feels like: Intense emotional reactivity. You feel things deeply and recover slowly. Social stress exhausts you for days. You’re prone to anxiety spirals. Your mood is unstable and context-dependent. You might feel fine one moment and devastated the next with minimal trigger. Small conflicts feel catastrophic. SSRIs often work very well for this variant because they directly compensate for the recycling defect.

TPH2 is the rate-limiting enzyme in serotonin synthesis. It converts tryptophan (an amino acid you eat) into 5-hydroxytryptophan, the first step toward making serotonin in the brain. Without sufficient TPH2 activity, you cannot manufacture serotonin regardless of how much tryptophan you consume. This is a production bottleneck.

Variants in TPH2 reduce this enzyme’s efficiency. About 20% of people carry functional variants that slow serotonin synthesis. If you have a TPH2 variant, you’re making serotonin at a fraction of normal capacity, and no amount of tryptophan-rich food or standard SSRI will fully compensate. You’re working with a fundamentally lower baseline.

What this feels like: Persistent low mood that doesn’t have an obvious trigger. Anhedonia; things that used to bring pleasure feel flat. Low energy and motivation. A heaviness that doesn’t lift with sleep or time off. SSRIs may help but often plateau at partial response because they can only recycle what little serotonin you’re producing. You feel like something is fundamentally missing.

GAD1 encodes glutamic acid decarboxylase, the enzyme that makes GABA (gamma-aminobutyric acid), your brain’s primary calming neurotransmitter. GABA is the off-switch for anxiety and rumination. Without it, your nervous system stays in constant activation. Serotonin works best when GABA is present to provide inhibitory tone; the two work synergistically.

Variants in GAD1 reduce GABA production by 20-30% in roughly 20-30% of people. When GAD1 function is impaired, you have less inhibitory tone in your nervous system, which means your anxiety systems are disproportionately active relative to your calming systems. You feel wired and stuck at the same time.

What this feels like: Anxiety without a clear source. Muscle tension, jaw clenching, racing thoughts at night. Your mood feels bottled up or trapped. Boosting serotonin alone doesn’t help because without GABA, serotonin can’t do its job. You may respond poorly to SSRIs alone because you need the calming signal, not just more neurotransmitter recycling. You might feel worse on stimulants.

MAOA is monoamine oxidase A, the enzyme responsible for breaking down serotonin, dopamine, and norepinephrine once they’ve done their job. It’s your neurotransmitter recycling manager. When MAOA works normally, it clears excess neurotransmitters so your nervous system doesn’t get overstimulated. When it’s slow, neurotransmitters accumulate.

The MAOA-L (low activity) variant is found in roughly 30-40% of males (females have two X chromosomes so the inheritance is more complex). If you carry MAOA-L, your serotonin, dopamine, and norepinephrine degrade more slowly, causing them to accumulate and create erratic mood and anxiety patterns. Your neurotransmitter levels fluctuate wildly rather than staying stable.

What this feels like: Your mood is unpredictable and reactive. You might feel fine, then suddenly irritable or overwhelmed by sensory input. Your stress response is heightened and slow to recover. You’re sensitive to stimulation; loud noise, bright lights, and social interaction deplete you faster than others. Caffeine and stimulants can push you into anxiety or irritability. You may have a history of impulsive behavior.

MTHFR is the enzyme that converts dietary folate into its usable form, methylfolate. Methylfolate is not just a B vitamin; it’s a critical cofactor for synthesizing serotonin, dopamine, and norepinephrine. Without efficient MTHFR function, your cells cannot produce the methyl groups needed to manufacture these neurotransmitters, no matter how much folate you eat.

The C677T variant reduces MTHFR efficiency by 40-70%. About 40% of people of European ancestry carry at least one copy. If you have a C677T variant, your cells are functionally folate-depleted, which directly impairs your ability to synthesize serotonin and dopamine at normal levels. You’re working with a neurotransmitter production system that’s missing a critical cofactor.

What this feels like: Low mood combined with cognitive symptoms: brain fog, poor memory, difficulty concentrating. You might also experience elevated homocysteine (which causes inflammation and further damages mood). Supplementing with regular folate doesn’t help because your MTHFR can’t convert it. Standard antidepressants may work partially but don’t address the root problem. You feel fundamentally depleted and foggy, not just sad.