Across 4 studies, all reported beneficial effects of Bifidobacterium bifidum Rosell-71 on depressive symptoms, with effect sizes ranging from small to moderate. The highest-quality evidence (a systematic review of 3,353 adults with psychiatric disorders) found a moderate beneficial effect. Evidence is predominantly from reviews and systematic reviews; no individual RCT data was extracted.
Caveats: 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). Evidence base is small (only 4 studies) — conclusions should be considered preliminary. All studies are reviews, not direct trials of the specific strain; effects may be confounded by multi-strain formulations. Only 1 of 4 studies reported a statistically significant finding, suggesting the observed benefit may be less robust than the effect direction implies.
There was a notably high measurement of effectiveness specifically in the treatment of depression symptoms.
Lactobacillus plantarum ... demonstrated particularly promising effects ... Psychobiotics show significant potential as adjunctive and therapeutic agents in depressive disorders through modulation of the gut-brain axis.
all demonstrating a significant amelioration of depression status after probiotic/psychobiotic treatment... In total, 7 out of 10 studies with probiotics as an add-on therapy ... exhibited a significant amelioration of depression status against placebo treatment.
This review explores the emerging field of hiPSCs and their potential in advancing microbiota-gut-brain axis science and depression research.