L-Methylfolate and Reduced Depression Symptoms

Across 3 studies, all reported beneficial effects of L-methylfolate on depression symptoms, with all findings statistically significant. Effect sizes are mixed (small to large), with the highest-quality evidence (a meta-analysis of 507 adults with MDD) showing a moderate effect (standardized mean difference = -0.38). The median study duration was 42 days, though only 1 of 3 studies reported duration; the most studied dose was 15 mg/day (from one small trial). Populations included adults with major depressive disorder and bipolar depression.

• Studied populations: adults with major depressive disorder or bipolar depression

Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Effect sizes vary widely across studies (small to large), and the largest effect came from a very small open-label trial (N=10); the meta-analysis provides the most reliable estimate with a moderate effect. Only one study reported dose and duration, limiting dose-response conclusions.