Gut microbiota and central nervous system's direct bidirectional regulation: The mechanisms of the gut–brain axis in irritable bowel syndrome

Abstract Background Irritable bowel syndrome (IBS) is a prevalent condition in which disrupted communication between the gut and the brain plays a central role in disease manifestation. A dynamic, bidirectional regulatory network links the gut microbiota with the central nervous system (CNS), commonly referred to as the gut–brain axis, and this network exerts broad influence over both gastrointestinal physiology and psychological states. Aims This review specifically concentrates on direct microbiota–CNS communication pathways in the context of IBS. Materials and Methods This narrative review synthesizes existing experimental and clinical evidence related to gut microbiota–brain interactions, with a particular focus on neural and neuroendocrine signaling mechanisms. Results Gut microorganisms affect CNS function via microbial metabolites and neural signalling routes, whereas the CNS modulates gastrointestinal activity through integrated neural and endocrine pathways, involving the autonomic nervous system and the enteric nervous system. Given the complexity of these reciprocal interactions, this review specifically concentrates on direct microbiota–CNS communication pathways, with particular attention to neural circuits and the hypothalamic–pituitary–adrenal axis in the context of IBS. Conclusion Furthermore, we discuss how advances in precision stratification and multi‐omics approaches may facilitate the development of personalized therapeutic strategies, ultimately improving symptom control and restoring balance between gut microbial ecosystems and neural regulation.