Omega-3 / Fish Oil for Depression
For depression, omega-3 helps only as an adjunct to standard treatment, and only when the formula is EPA-dominant and dosed high enough; it is not a standalone cure, and DHA-heavy products do nothing.
Why this grade7-layer evidence engine
The evidence earns a Preliminary (Tier B) grade because benefit is real but narrowly conditional. A high-quality 2019 meta-analysis (PMID 31383846, n=2,160) found a modest pooled effect (SMD -0.28) that grew much larger for EPA-pure (SMD -0.50) and EPA-major formulas (SMD -1.03), while DHA-dominant products showed no benefit over placebo. This formulation split is the single most important caveat.
Dose and patient type matter just as much. A government-funded dose-finding RCT (PMID 36005883) saw a meaningful response only at EPA 4 g/day (Cohen d=0.53), with 1-2 g/day no better than placebo and the effect concentrated in patients with high inflammation. A 2025 review (PMID 39912390) echoed that higher-EPA doses help most in inflammatory, late-life, or cardiac-comorbid depression. In children and adolescents, a 2024 systematic review (PMID 39564892) found no significant effect (very low certainty).
It is not Tier A because no major regulator (FDA, EFSA, NHS, WHO) authorizes any depression claim, and clinical bodies stay cautious: Mayo Clinic states fish oil alone is not a depression treatment, while Harvard, Cleveland Clinic, and the ADAA frame EPA-rich omega-3 (about 1-2 g/day, EPA >=60%) as an adjunct alongside, not instead of, proven therapy. Evidence also points against using it to prevent 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 = 0.595
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (1 positive vs 1 negative)，由 raw_score 決定
- 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