Methylation Explained Simply — What It Is and Why It Drives Your Mental State

Methylation in one sentence — and one analogy

Methylation is the process by which the body "attaches" a small methyl group (-CH3) to another molecule. This simple act happens billions of times per second in every cell and governs:

• switching genes on and off (epigenetics)
• the production and breakdown of neurotransmitters (serotonin, dopamine, melatonin)
• histamine breakdown
• liver detoxification
• myelin formation (nerve insulation)
• immune regulatory processes

An analogy that resonates with people: picture the body as a massive factory. Methylation is the labeling system the factory uses to route packages ("this molecule goes left, that one goes right, this one gets broken down, this one gets stored"). If labels are missing or attached incorrectly, packages go to the wrong place — and the factory's system falls into disarray. This is exactly how methylation imbalances show up: as quiet chaos across dozens of processes at once.

The SAM cycle — where methyl groups come from

The body doesn't stockpile methyl groups. It produces them through a cyclical process called the SAM cycle (or methionine cycle). It works like this:

1. Methionine (an amino acid, found mainly in meat, eggs, and fish) is converted in the liver into SAM (S-adenosylmethionine) — the "charged" methyl group donor.

2. SAM donates its methyl group to a recipient (for example, histamine that the body wants to break down, or a gene it wants to switch off). After donating, SAM becomes SAH (S-adenosylhomocysteine) — the "discharged" form.

3. SAH breaks down into homocysteine, which is then either recycled back into methionine (with the help of B12 and folate), or diverted into transsulfuration to form glutathione (the body's most important antioxidant).

Two things matter for psychiatry: high SAM = strong methylation, high SAH = a brake on methylation. And the SAM/SAH ratio itself is more precise than either number alone.

Why methylation controls neurotransmitters: SERT and DAT

This is where methylation meets psychiatry. The brain has two very important "vacuums" in the synapses:

• SERT — the serotonin transporter, which pulls serotonin out of the synaptic gap back into the cell
• DAT — the dopamine transporter, which does the same for dopamine

Methylation directly controls how many of these transporters are present in synapses. In undermethylation, there are more of them and they are more active — serotonin disappears from the synapse too quickly, the signal is weak. In overmethylation, there are fewer of them, and serotonin lingers in the synapse too long — paradoxically causing anxiety and overstimulation.

This is precisely why SSRI antidepressants (which block SERT) help undermethylators and worsen overmethylators. It isn't a matter of dose — it's a matter of biochemical biotype.

Undermethylation: typical symptoms

Undermethylation is the most common methylation pattern in depression — Walsh's data suggest a prevalence of around 38% among depressed patients. The mechanism behind the symptoms: low SAM availability + elevated SAH + accelerated reuptake of serotonin and dopamine via SERT/DAT overexpression. The result is lower functional activity of both neurotransmitters, even though overall production may be normal.

Mental and behavioral signs:

• chronic depression beginning in childhood or adolescence
• strong outward discipline and self-control, with intense inner tension
• perfectionism, competitiveness, a "type A" personality
• obsessive thinking or ritualized behavior
• strong academic / professional performance, a "workaholic" type
• higher libido compared to peers
• irritability or anger under pressure
• rigidity, dependence on routine

Physical and pharmacological signs:

• seasonal allergies or chronic nasal congestion
• good initial response to SSRIs, later followed by emotional flattening or "leveling out"
• good response to antihistamines (cetirizine, loratadine)
• poor response to benzodiazepines — they don't bring the expected calming effect
• total whole-blood histamine >70 ng/ml
• tendency toward migraines, fatigue, skin issues (inflammation as an accompanying feature)

Overmethylation: typical symptoms

Overmethylation is less common than undermethylation, but clinically very important — these clients respond in the opposite way to standard depression treatment and are often misclassified as an anxiety disorder or even psychosis.

Mental and behavioral signs:

• high anxiety, panic, paranoid thoughts
• chemical sensitivity, sensitivity to smells, light, and noise
• restless, "racing" thoughts
• artistic and creative type, high empathy
• often an emotionally "unstable" response — strong swings

Physical and pharmacological signs:

• absence of seasonal allergies
• dry eyes and dry mouth
• higher pain threshold
• worsening after SSRIs (anxiety, panic, akathisia)
• no improvement from antihistamines, paradoxically
• total whole-blood histamine <40 ng/ml

Blood histamine — a secondary but practical marker

Whole-blood histamine level is an indirect indicator of methylation. The logic is simple: histamine is broken down in the body by the enzyme HNMT, which uses SAM as a cofactor. Weak methylation = insufficient SAM = histamine breaks down slowly = higher blood levels.

This gave rise to Walsh's practical classification: >70 ng/ml = undermethylation, <40 ng/ml = overmethylation. For most clients, this test is sufficient — it is cheaper and clinically validated across tens of thousands of cases.

For a more precise measurement of methylation itself, the plasma SAM/SAH panel exists (details in the article Whole-Blood Histamine vs. Plasma Methylation Test). We use it when histamine falls in the "gray" range, or when the clinical picture doesn't match.

What an MTHFR test WON'T tell you

Many people today order the genetic MTHFR test (C677T, A1298C) hoping it will explain their depression. Walsh's view is more sober: genetics shows only potential, not current function.

A person with an MTHFR mutation may methylate completely normally — the body has dozens of compensatory mechanisms (alternative pathways, other enzymes, BHMT, the betaine shuttle). Conversely, a person with no mutation at all can be a severe undermethylator if they have chronic stress, inflammation, alcohol use, or cofactor deficiencies.

In practice: a functional test (blood histamine, SAM/SAH panel) is far more accurate than genotype. Recommending methylfolate based on an MTHFR mutation alone can make some clients (especially undermethylators) feel worse. Folate can actually worsen depression in undermethylation — explained in the article Folate Can Worsen Depression.

How functional methylation is tested

For psychiatric indications, we recommend a stepwise approach:

1. Free 5-minute screening — indicates which biotype you likely fall into (for orientation only, not a diagnosis).

2. Whole-blood histamine (€149) — the primary marker. Sufficient for most clients to distinguish undermethylation from overmethylation.

3. Plasma methylation panel — for gray-zone histamine results, poor tolerance of standard treatment, or suspected SAH/homocysteine blockage.

4. Contextual markers — copper, ceruloplasmin, zinc, vitamin D, B12, ferritin. These help interpret the overall picture.

5. 45-minute consultation (€75) — we review the results and explain the individual values; nutritional support and the plan are handled in the Consultation with a Doctor / Therapist (€149).

Without testing, we remain in the realm of guesswork. In psychiatry, that means years of switching medications with no clear logic. Methylation testing can bring that logic back.

Why these tests together give a picture no single test can

Each test alone shows only one layer of the picture. Combined, they produce something different — a complete map you can actually work with. Specifically:

• Blood histamine shows whether methylation is outwardly fast or slow — and therefore whether you tend toward an undermethylation or overmethylation biotype.
• The SAM/SAH panel shows what's happening inside the cycle — whether methylation is starting slowly, or whether it's "blocked from below" via high SAH.
• Homocysteine shows whether the cycle can close and return to methionine, or whether it gets stuck.
• Copper, zinc, ceruloplasmin show whether the necessary cofactors are present — without which methylation cannot function properly, even if everything else is fine.

The combination of these markers can answer four practical questions: (1) is your methylation running slow or fast, (2) are your neurotransmitter transporters overexpressed or suppressed, (3) is inflammation or external toxins putting pressure on methylation, (4) are the nutritional cofactors needed to produce SAM missing. These four answers then determine what makes sense in treatment — and what doesn't.