Probiotic depression findings depended on which trials were included
Average symptom scores favored probiotics, but the result was no longer statistically clear after selected studies were excluded.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
For adults with depression who were not taking psychotropic medication, the main analysis found a small average symptom improvement with probiotics compared with placebo. However, analyses excluding industry-funded studies or those using additional agents did not retain statistical significance. The findings therefore depend on which studies are included and remain uncertain.
This abstract-based summary concerns a small, varied evidence base. Possible funding-related bias and additional agents complicate the claim about probiotics alone; treatment duration is not reported.
What researchers found
Change in depression rating scores
Probiotics versus placebo; assessment timeframe unreported. SMD measures differences in standard-deviation units, not depression-scale points. Negative values mean lower symptom scores with probiotics. The confidence interval gives an uncertainty range entirely below zero (no difference).
Symptoms and side effects
Researchers assessed changes on validated depression rating scales. Minor side effects did not differ statistically between groups, and no serious adverse events were reported. These reports do not establish safety for every patient.
Why exclusions mattered
Sensitivity analyses checked whether the symptom finding held after selected studies were removed. The loss of statistical significance does not prove that probiotics lack an effect; it shows uncertainty about the overall finding.
The original publication
Efficacy of probiotic intervention in unmedicated depression: a systematic review and meta-analysis.
Haiyan L, Dan W, Xiaochao W et al.
Front Psychiatry · 2025
- PubMed ID
- 41573044
- Record checked
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