Research Advances in Modulation of Psychological Stress and Related Anxiety and Depression by Probiotics and Postbiotics

Neuroendocrine homeostatic imbalance induced by psychological stress is closely associated with gut microbiota dysbiosis, which consequently increases the susceptibility to mental disorders such as anxiety and depression. In recent years, targeting the microbiota-gut-brain axis has emerged as a novel strategy for the intervention of stress-related psychosomatic symptoms. Latest research progress of psychobiotics and postbiotics in alleviating psychological stress and improving anxiety and depression were summarized, focusing on elucidating the specific differences in their mechanisms of action. Acting as active bioreactors, the functions of probiotics are highly dependent on their intestinal colonization ability and metabolic activity. Probiotics can synthesize short-chain fatty acids and neuroactive compounds (such as γ-aminobutyric acid and serotonin) in situ, and activate the vagal afferent pathway to achieve negative feedback regulation of the central nervous system. In contrast, postbiotics act as immunomodulatory signals. They rely on retained microbe-associated molecular patterns (such as cell wall components like lipoteichoic acid) to directly interact with host receptors, inducing anti-inflammatory responses to alleviate systemic inflammation, and repairing the intestinal barrier by upregulating tight junction proteins to block endotoxin translocation. The sources and influencing factors of heterogeneity in current clinical research results were analyzed and the limitations faced by postbiotics in practical applications were discussed. The challenges in the research direction of targeted microecological regulation for intervening in psychological stress, including the elucidation of strain-specific mechanisms of action, the exploration of functional postbiotic components, and the standardization of clinical applications were dissected. This review aimed to provide a theoretical reference for the development of functional foods targeting the microbiota-gut-brain axis and the establishment of nutritional adjuvant intervention strategies for psychological stress-related mental disorders.