Add-on Limosilactobacillus reuteri probiotic does not reduce depressive symptoms in overweight depressed patients with systemic low-grade inflammation
In an 8-week double-blind RCT, 75 patients with major depressive disorder, BMI ≥25 kg/m2, and hs-CRP ≥1 mg/L received either L. reuteri probiotic or placebo added to stable treatment. No significant effects were found on any primary or secondary outcomes (all p > 0.25). Lower baseline fecal formic acid and greater treatment-associated increase in fecal formic acid were significantly associated with MADRS score reduction in the probiotics group (p < 0.01).
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Add-on Limosilactobacillus reuteri probiotic does not reduce depressive symptoms in overweight depressed patients with systemic low-grade inflammation The current body of evidence comprises 1 study, including 1 randomized controlled trial. EvidenceHub rates the overall confidence at 48/100 (low).
The Claim
Add-on Limosilactobacillus reuteri probiotic does not reduce depressive symptoms in overweight depressed patients with systemic low-grade inflammation
This conclusion is most relevant to: Overweight (BMI ≥25 kg/m2) patients with major depressive disorder and systemic low-grade inflammation (hs-CRP ≥1 mg/L).
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸Add-on probiotics for inflammatory depression - A double-blind randomized placebo-controlled trial. (Brain, behavior, and immunity, 2025) —
How It Works
The proposed biological pathway:
- ▸Probiotic supplementation increases fecal formic acid levels
- ▸Formic acid has anti-inflammatory properties
- ▸Lower baseline formic acid and greater increase in formic acid correlate with depression improvement
- ▸Result: Preliminary evidence for formic acid as a biomarker and possible mediator of treatment response
Who Might Benefit
Evidence fit by population:
- ▸Overweight (BMI ≥25 kg/m2) patients with major depressive disorder and systemic low-grade inflammation (hs-CRP ≥1 mg/L)
Recommended Dose
N/A (specific dose not reported in abstract)
Limitations & Caveats
Important context when interpreting this evidence:
- ▸No overall antidepressant effect observed, limiting generalizability
- ▸Preliminary evidence for formic acid as mediator requires further validation
- ▸Modified intention-to-treat analysis may introduce bias
Frequently Asked Questions
Did the probiotic improve depression in this study?▼
No, there were no significant effects of probiotics relative to placebo on any primary or secondary outcomes.
What was the role of formic acid in this study?▼
Lower baseline levels and a greater increase in fecal formic acid were significantly associated with depression improvement in the probiotics group, suggesting it may be a biomarker or mediator.
Who was eligible for this trial?▼
Patients with major depressive disorder, BMI ≥25 kg/m2, and high-sensitivity C-reactive protein ≥1 mg/L.
What type of probiotic was used?▼
Limosilactobacillus reuteri (L. reuteri) probiotic supplement.
References
- 1.Söderberg Veibäck G, Lindahl J, Suneson K, Tjernberg J, Ståhl D, Landberg R, Asp M, Kjellberg A, Falknäs F, Sjöberg K, Lavebratt C, Wolkowitz OM, Lindqvist D. “Add-on probiotics for inflammatory depression - A double-blind randomized placebo-controlled trial..” Brain, behavior, and immunity, 2025. PMID: 40484149 DOI: 10.1016/j.bbi.2025.06.002