THE GUT-BRAIN AXIS: EXPLORING THE IMPACT OF GUT MICROBIOTA ON MENTAL HEALTH

Abstract

The microbiota-gut-brain axis represents a complex bidirectional communication network linking the intestinal microbiota with the central nervous system through neural, endocrine, immune, and metabolic pathways. Growing evidence suggests that alterations in gut microbiota composition may contribute to the pathophysiology of several mental disorders, including depression, anxiety disorders, bipolar disorder, and attention-deficit/hyperactivity disorder. This review aims to summarize current knowledge on the mechanisms by which gut microbiota may influence mental health and to discuss microbiota-targeted therapeutic approaches. Dysbiosis may affect brain function through vagus nerve signaling, hypothalamic-pituitary-adrenal axis activation, increased intestinal permeability, systemic inflammation, cytokine release, altered neurotransmitter metabolism, and reduced production of short-chain fatty acids. Studies indicate that individuals with psychiatric disorders often show reduced microbial diversity, depletion of beneficial anti-inflammatory and butyrate-producing bacteria, and enrichment of pro-inflammatory microbial taxa. These changes may promote neuroinflammation, oxidative stress, impaired stress regulation, and disturbances in serotonin, dopamine, gamma-aminobutyric acid, and tryptophan-related pathways. The review also examines the potential role of probiotics, prebiotics, synbiotics and fecal microbiota transplantation in modulating the gut microbiome and improving psychiatric symptoms. Although some clinical and experimental findings suggest beneficial effects, especially in depression and anxiety, the available evidence remains heterogeneous. Further well-designed, long-term clinical studies, are recquired to clarify causal mechanisms, identify effective microbial interventions, and determine their place in mental health prevention and treatment.