Research synthesisLow evidenceModerate effect3 studies · 3 beneficial · 0 neutral · 0 harmful
Across 3 studies (all systematic reviews or meta-analyses), all reported moderate beneficial effects of Bifidobacterium plantarum-containing probiotics on depressive symptoms, with 2 reaching statistical significance. The evidence is preliminary and predominantly based on multi-strain formulations, making the specific contribution of Bifidobacterium plantarum unclear. Effect sizes were consistently moderate, but no consistent dose, form, or population was identified.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). The studies often used multi-strain probiotic formulas or different species (e.g., Lactobacillus plantarum), so the specific effect of Bifidobacterium plantarum alone is uncertain. The meta-analysis reported high heterogeneity (I² = 79%), indicating considerable variability across trials.
Generated Jun 11, 2026