Evaluating the efficacy of probiotics in schizophrenia and depression: A meta-analysis of clinical outcomes and subgroup effects

Abstract

Background

Schizophrenia and depression are disabling mental disease conditions that have multifactorial pathophysiology involving the dysregulation of the gut–brain axis. Probiotics have been advocated as an adjunct therapy that could have an impact on psychiatric symptoms by normalizing the gut immune mechanisms.

Aims

This meta-analysis evaluated whether probiotic supplementation improves psychiatric symptoms in patients with schizophrenia or depression.

Methodology

A systematic search of multiple databases identified randomized controlled trials (RCTs) that tested probiotic interventions in these populations. Eligible studies were analyzed for pooled effect sizes, heterogeneity, and publication bias.

Findings

Thirteen RCTs (n = 893 participants) were included. Meta-analysis revealed no significant difference in PANSS score reduction between probiotic and placebo groups of schizophrenia patients (P = .546). However, a significant pooled standardized mean difference between intervention and control groups was found (P = .043). Significant heterogeneity was observed, and subgroup analyses indicated variations in outcomes based on geographic region and ethnicity. A potential moderating effect of vitamin D status was identified as a factor requiring future study.

Conclusion

Currently, there is no evidence that probiotics consistently improve depression or schizophrenia. The significance of subgroup analysis raises questions and emphasizes the necessity of carefully planned, sufficiently powered studies to determine whether probiotic efficacy is influenced by particular populations, settings, or supplemental techniques.