Probiotics for Depression
Verdict: Published with Warning
Across 4 PubMed studies, the evidence for Probiotics in Depression grades Tier C — weak evidence. Effective, but with safety or population caveats.
C 🟠 C Weak Evidence Published with Warning
Why this grade7-layer evidence engine
⚖️
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.49
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
C · Published with Warning
Confidence
67%
Broadly consistent
Evidence level
E2
Multiple high-quality MAs (≥2 independent, consistent)
▸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 = 0.487
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 1 negative)
- 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
PubMed studies (4)L2 · primary research & systematic reviews
Effects of Prebiotics and Probiotics on Symptoms of Depression and Anxiety in Clinically Diagnosed Samples: Systematic Review and Meta-analysis of Randomized Controlled Trials
Finding: Probiotics significantly reduced depression symptoms across 23 RCTs (SMD -0.96, 95% CI -1.31 to -0.61); prebiotics showed a nonsignificant trend.
View on PubMed A systematic review of the effects of probiotics on depression and anxiety: an alternative therapy?
Finding: Narrative SR of 9 double/triple-blind placebo-controlled RCTs judged probiotic benefit for depression/anxiety promising but still preliminary.
View on PubMed Clinical, gut microbial and neural effects of a probiotic add-on therapy in depressed patients: a randomized controlled trial
Finding: 31-day add-on probiotic RCT (n=47 completers) showed a stronger HAM-D decrease over time in the probiotic group vs placebo, alongside gut microbiota and neural changes.
View on PubMed Updated Review and Meta-Analysis of Probiotics for the Treatment of Clinical Depression: Adjunctive vs. Stand-Alone Treatment
Finding: MA of 7 RCTs (n=404): probiotics effective as adjunct to antidepressants (SMD 0.83, 95% CI 0.49-1.17) but showed no significant benefit as stand-alone treatment (SMD -0.02, 95% CI -0.34 to 0.30).
View on PubMed Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …
L4a US FDA
Cautious
FDA has not approved any probiotic product for use as a drug or biological product in infants of any age source↗
L4b EU EFSA
Against
a cause and effect relationship had not been established between the consumption of a combination of bacterial strains and reduction of gastro-intestinal discomfort source↗
L4c UK NHS
Cautious
There's some evidence that probiotics may be helpful in some cases, such as helping to ease some symptoms of irritable bowel syndrome (IBS). But there's little evidence to support many health claims made about them. source↗
L4d TW TFDA / 衛福部
Supportive
益生菌屬食品，並無治療疾病的效果 source↗
L4e WHO
Neutral
probiotic supplementation with the strains Bifidobacterium longum subsp. Infantis DSM33361 and Lactobacillus rhamnosus GG source↗
L5a NIH Office of Dietary Supplements
Supportive
Probiotics might reduce some symptoms of IBS. source↗
L5b Mayo Clinic
Neutral
L5c Cleveland Clinic
Neutral
Nutritional supplements: Omega-3 fatty acids (fish oil), SAMe and probiotics source↗
L5d Harvard Health
Cautious
The results of these studies were mixed; some suggested that there may be mild benefits... There are no compelling data that suggest a true benefit source↗
L5e Specialty Society (condition-mapped)
Not addressed