Alcohol use disorder is a chronic relapsing condition with significant neurobiological, psychological, and social implications. Relapse, defined as the resumption of clinically significant alcohol consumption following abstinence, represents a major barrier to sustained recovery. Emerging evidence indicates that the gut-brain axis may contribute to relapse vulnerability through persistent peripheral and central biological alterations. Chronic alcohol consumption can induce intestinal dysbiosis and disrupt epithelial integrity. This increases intestinal permeability and facilitates the translocation of bacterial endotoxins. These processes may promote systemic inflammation and sustained neuroimmune activation. Also, this can alter glutamatergic, dopaminergic, and GABAergic signaling pathways involved in cravings, negative emotions, and stress sensitivity. Alcohol-related dysbiosis also modifies microbial metabolites, including short-chain fatty acids and tryptophan catabolites, potentially reinforcing inflammatory and neurochemical imbalances. Comorbid depression may further amplify these interactions by enhancing pro-inflammatory signaling and emotional dysregulation. This could increase the risk of relapse. Preclinical studies suggest that microbiota-targeted interventions, such as strain-specific probiotics, fecal microbiota transplantation, and postbiotics including butyrate derivatives, can restore intestinal barrier function, attenuate neuroinflammation, and reduce relapse-like behaviors in experimental models. However, clinical translation remains limited, and longitudinal studies specifically evaluating relapse outcomes are insufficient. This narrative review integrates mechanistic and translational evidence linking gut dysbiosis, intestinal barrier dysfunction, systemic inflammation, and neuroimmune activation to relapse vulnerability in AUD. By situating relapse within an integrated gut-brain framework, we propose that microbiota-informed strategies may represent promising adjunctive approaches to complement existing relapse-prevention treatments.
