Across 4 studies (all systematic reviews or reviews), all reported beneficial effects of Bifidobacterium bifidum Rosell-71 on depressive symptoms, with a predominantly moderate effect size. Only 1 study reported statistically significant findings. The most studied populations were adults with psychiatric and cognitive disorders, though no specific dose or duration was consistently reported.
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. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests.
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.