Across all 3 available studies, beneficial but small effects of Bifidobacterium bifidum Rosell-71 on mental health were reported, though none reached statistical significance. The evidence base is limited to review articles rather than direct interventional trials, and no specific dose, form, or study duration was consistently reported.
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). Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests.
it appears that probiotics have a beneficial effect on mental health, cognitive functions, sleep, gastrointestinal, and upper respiratory symptoms in adult humans.
Ten studies investigated the same combination of probiotics and provided evidence to support the claims made. Statistically significant results were not universally present for all products.
Psychobiotics are probiotics that contribute beneficially to the brain function and the host mental health... the potential therapeutic effects of the psychobiotics alone or in combination with conventional medicine in the treatment of... some psychiatric diseases like depression, schizophrenia, and bipolar disorder