Methylfolate helps with depression

Adding methylfolate to an antidepressant has produced a small improvement in depression in a handful of controlled trials, mostly at a prescription-strength dose of 15 mg a day. A 2022 review that pooled these trials described the effect as small, and a 2018 review rated all of the evidence low or very low in quality. No placebo-controlled trial has tested methylfolate on its own as a treatment for depression.

The most important qualifier is what was tested. In the trials with the clearest results, 15 mg a day was added for one to six months to the treatment of adults with diagnosed depression, under medical care, and in the 2012 trials the antidepressant had not worked well enough on its own. No placebo-controlled trial has tested methylfolate in milder low mood without a diagnosis, in children or adolescents, in pregnancy or breastfeeding, or in bipolar depression. The 15 mg dose is far above the 1,000 microgram daily upper limit the US Institute of Medicine set for folate from supplements, a limit based on case reports of people with vitamin B12 deficiency whose nerve damage developed or progressed while they took folate. The US label for a prescription methylfolate product advises caution in people with a history of bipolar illness and lists interactions with anti-seizure medicines.

The clearest result comes from two trials published together in 2012, in 223 outpatients whose depression had not lifted on an SSRI antidepressant. In the trial that gave 15 mg a day, more people improved with methylfolate than with placebo, about one extra person for every six treated; in the trial that started at half that dose, there was no difference. Both trials were funded by Pamlab, a company that sold a prescription methylfolate product. An earlier trial, published in 1990, gave 15 mg a day for 6 months alongside usual treatment to 41 people with depression or schizophrenia and low folate, and their recovery was better than with placebo. An international psychiatry taskforce in 2022 provisionally recommended 15 mg of methylfolate a day as an add-on in major depression, and did not recommend folic acid.

Other trials answer narrower questions. In 96 older adults with dementia, depression and normal folate levels, 50 mg a day of methylfolate taken on its own lowered depression scores by about as much as the antidepressant trazodone over 8 weeks; with no placebo group, the trial shows similar change on both treatments, not how much of it either treatment caused. A 2025 open-label trial in Pakistan gave a much lower dose, 800 micrograms a day, alongside antidepressants to 44 people aged 14 and over, assigned to groups without randomization; symptom scores fell by 40% with methylfolate and 26% without, and remission rates did not differ significantly. A UK trial in 475 adults that used folic acid rather than methylfolate found no added benefit over placebo.

In the 2012 trials, side effects were reported no more often with methylfolate than with placebo. The prescription label's bipolar caution rests on the possibility of mood elevation, and its interaction list says anti-seizure medicines such as phenytoin, carbamazepine and valproic acid lower folate absorption, and that folic acid has been linked to faster breakdown of phenytoin. Whether methylfolate fits alongside a particular antidepressant or other medicine is a conversation with the reader's clinician.

Methylfolate is the form of folate that circulates in the blood. Folate feeds the body's methylation cycle, which makes S-adenosylmethionine (SAMe), and it is linked to the cofactor needed to make serotonin, dopamine and noradrenaline. In a 2000 study of 46 severely depressed inpatients, those with raised homocysteine, a blood marker of low functional folate or vitamin B12, had lower folate, SAMe and breakdown products of these messengers in the fluid around the brain and spinal cord. Whether extra methylfolate changes these pathways in people whose folate is already normal has not been shown; the 1990 trial enrolled only people with low folate, and in the 2025 trial only people below a set blood folate level were given methylfolate.