Efficacy of prebiotics, probiotics, and postbiotics on depression: a systematic review and meta-analysis of randomized controlled trials

Why clinicians should know about it

• Picked for Microbiology (medical) (top studies of the week, 26 July 2026).

Abstract

BACKGROUND: Depression is a global health issue linked to gut-microbiota-dysbiosis, which influences brain function through the gut-brain axis. Dietary biotics offer a promising therapeutic avenue. OBJECTIVE: This systematic review and meta-analysis aimed to evaluate the efficacy of biotic interventions in managing depression. METHODOLOGY: Five databases were searched for randomized controlled trials (RCTs) from 2016 to 2024. 27 RCTs with a control group and standard depression rating scales were included. Data extraction and risk-of-bias assessment were conducted independently by two reviewers, with certainty-of-evidence appraised using GRADE. Meta-analyses employed standardized mean differences, with subgroup analyses by intervention duration (short: <6 weeks, medium: 6-12 weeks, and long: >12 weeks), respectively. RESULTS: Probiotic interventions showed no significant effects in short and medium-duration subgroups (6 and 12 studies, respectively), both of which demonstrated substantial heterogeneity. A significant effect was observed in the long-duration subgroup (2 studies) with no observed heterogeneity, although based on limited evidence. Prebiotic interventions showed no significant effects, while postbiotic interventions demonstrated no clear effects across durations, with variable heterogeneity. Sensitivity analyses were generally consistent with the main findings. Overall certainty of evidence was rated as moderate due to inconsistency across studies. CONCLUSION: Probiotics administered over longer durations may be associated with improvements in depressive symptoms, although this finding is based on limited evidence. Evidence for prebiotic and postbiotic interventions remains inconclusive. Overall, substantial heterogeneity was observed across studies, and findings should be interpreted cautiously. Further well-designed randomized controlled trials are needed to clarify the effects of microbiome-targeted interventions in depression.

Abstract as published, via PubMed.