Probiotic trials reported modest, variable improvements in major depression
Symptom improvements varied across trials, with the clearest pattern among outpatients with mild-to-moderate depression receiving formulations containing several bacterial strains.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
The review describes modest symptom improvements when probiotics were studied as an additional treatment for diagnosed major depression. Results varied across patient settings and formulations, and the abstract does not provide a pooled symptom effect. The findings therefore do not establish a broadly effective product or show that probiotics can replace depression treatment.
Differences between methods, participant dropout and selective reporting remained concerns despite mostly low risk-of-bias ratings. The abstract supplies no pooled symptom effect or long-term follow-up, limiting estimates of benefit size and persistence.
Where results clustered
Improvements were reported most often in outpatients with mild-to-moderate depression receiving products that contained several bacterial strains. This pattern across trials does not show that these formulations outperform other probiotics in a direct comparison.
Beyond depressive symptoms
Findings for cognition, inflammation, metabolism and gastrointestinal outcomes varied. The authors described probiotics as generally well tolerated, but the abstract supplies no detailed adverse-event counts or evidence about sustained benefit after treatment ends.
The original publication
The therapeutic readiness of probiotics in major depressive disorder: A systematic review of randomised controlled trials.
Johnson D, Ramachandram DS, Doorly J et al.
J Psychopharmacol · 2026
- PubMed ID
- 41453849
- Record checked
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