Association between gut microbiota and anxiety disorders: a bidirectional two-sample Mendelian randomization study

Abstract Background There are many articles reporting that the component of intestinal microbiota implies a link to anxiety disorders (AD), and the brain-gut axis is also a hot topic in current research. However, the specific relevance between gut microbiota and AD is uncertain. We aimed to investigate causal relationship between gut microbiota and AD by using bidirectional Mendelian randomization (MR). Methods Genetic instrumental variable (IV) for the gut microbiota were obtained from a genome-wide association study (GWAS) involving 18,340 participants. Summary data for AD were derived from the GWAS and included 158,565 cases and 300,995 controls. We applied the inverse variance weighting (IVW) method as the main analysis. To ensure the robustness of the results, we further executed weighted median method and MR-Egger regression to evaluate potential horizontal pleiotropy. Result We discovered 16 potential connections between bacterial traits and AD. Utilizing the IVW method, we identified 7 species that exhibited a direct correlation with the risk of AD: class Negativicutes, genus Eubacteriumbrachygroup, genus Coprococcus3, genus Enterorhabdus, genus Oxalobacter, genus Ruminiclostridium6, order Selenomonadales. Additionally, we found 9 species that exhibited a negative association with AD: class Methanobacteria, family Methanobacteriaceae, family Porphyromonadaceae, genus Blautia, genus Butyricicoccus, genus Erysipelotrichaceae-UCG003, genus Parasutterella, order Methanobacteriales, phylum Proteobacteria. Conclusion Our study found a causal relation between parts of the gut microbiota and AD. Further randomized controlled trials are crucial to elucidate the protective effects of probiotics on AD and their particular protection systems.