Global Meta-Analysis of the Gut-Brain Axis: Unveiling the Impact of Microbiome Alterations on Psychiatric Disorders

Background : Emerging research suggests a significant connection between the gut microbiome and mental health, termed the ”gut-brain axis.” However, findings across studies are inconsistent, and no comprehensive meta-analysis has quantified this relationship globally. Objective : To systematically review and meta-analyze existing literature on the association between gut microbiome alterations and psychiatric disorders, identifying specific microbial profiles linked to different mental health conditions. Methods : A systematic review was conducted across multiple databases for studies examining the gut microbiome in patients with psychiatric disorders compared to healthy controls. Data on microbial diversity, specific bacterial taxa, and psychiatric outcomes were extracted. Meta-analytic techniques were used to pool data and assess the strength of associations, with adjustments to include studies with varying designs and data availability. Results : We identified 50 studies encompassing a total of 4,237 participants from various geographic regions. Meta-analysis revealed that patients with psychiatric disorders exhibited significantly reduced alpha diversity (standardized mean difference [SMD] = -0.45; 95% CI: -0.52 to -0.38; p < 0.001) compared to controls. Specific microbial taxa, such as decreased Faecalibacterium prausnitzii (SMD = -0.65; 95% CI:-0.75 to -0.55; p < 0.001), were consistently associated with conditions like depression and schizophrenia. Conclusion : This comprehensive meta-analysis clarifies the role of the gut microbiome in psychiatric disorders, revealing consistent patterns of microbial alterations. These findings have potential implications for developing microbiome-based diagnostics and therapeutic interventions targeting the gut-brain axis.