L-Tyrosine for Depression
L-tyrosine does not appear to relieve depression. Despite being a precursor to dopamine and other catecholamines, the only controlled trial found no antidepressant benefit, so it should not be used to treat depression.
Why this grade7-layer evidence engine
The grade reflects direct counter-evidence rather than a simple lack of data. The single double-blind randomized controlled trial (PMID 2142699; Gelenberg 1990, n=65, 4 weeks, tyrosine vs. imipramine vs. placebo) found no antidepressant activity: tyrosine raised MHPG excretion, a catecholamine marker, but this biochemical change did not translate into clinical improvement. The only positive signals come from an uncontrolled 1982 narrative review (PMID 6764934) and a 1980 Lancet letter (PMID 6107536), both low-quality and superseded by the negative trial.
Regulators support safety, not efficacy. The US FDA lists L-tyrosine only as a permitted nutrient supplement and flavoring agent, granting no health claim for mood. EFSA accepts that tyrosine contributes to normal dopamine and catecholamine synthesis in a protein-adequate diet, but this is a physiological precursor statement, not evidence of antidepressant effect, and EFSA notes typical European diets already supply enough protein. The UK NHS cannot recommend tyrosine supplementation, citing inadequate efficacy and safety outcome data.
Clinical guidance is essentially silent: major centers and psychiatric bodies do not endorse tyrosine for depression. The evidence base is also old (1980-1990) with no modern RCT or meta-analysis. One safety caution matters here: combining tyrosine with MAOI antidepressants carries a risk of hypertensive crisis, which is relevant for people being treated for depression.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.306
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 無高階證據可裁決
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status