Brain–Gut Axis Perspective on Irritable Bowel Syndrome: The Role of Gut Microbiota and Therapeutic Strategies of Traditional Chinese Medicine

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, with dysfunction of the gut–brain axis (GBA) being its core pathogenic mechanism. Traditional Chinese Medicine (TCM), guided by the theory of “liver–spleen interaction” and the core therapeutic principle of “soothing the liver and invigorating the spleen”, has accumulated extensive clinical experience in IBS treatment. This review systematically searched PubMed, Web of Science, and CNKI databases to summarize the molecular mechanisms by which gut microbiota participate in IBS pathogenesis through the GBA, interpret the modern biological connotation of the TCM pathogenesis of “liver depression and spleen deficiency” from the perspective of the GBA, and review the evidence for TCM in treating IBS by modulating gut microbiota. The results indicate that gut microbiota dysbiosis drives IBS symptoms through three major metabolic pathways — short-chain fatty acids, bile acids, and 5-hydroxytryptamine — and achieves bidirectional regulation via the GBA. TCM monomers (e.g., berberine, curcumin, apigenin), single herbs (e.g., Atractylodes, Cinnamomum, Liupao tea), classical formulas (e.g., Tong-Xie-Yao-Fang, Chang-Kang-Fang, Si-Ni-San), as well as acupuncture and moxibustion, may improve IBS symptoms by restoring gut microbial diversity, regulating metabolite levels, repairing the intestinal barrier, and inhibiting inflammatory pathways. TCM may offer unique advantages in treating IBS through multi-target regulation of gut microbiota. Future research should focus on the objectification of TCM syndrome differentiation based on gut microbiota and the development of precision matching strategies.