Abstract: Journal of Psychiatry and Neurochemistry Research

Abstract:
The gut-brain axis is a complex bidirectional communication system between the gastrointestinal tract and the central nervous system, involving neural, hormonal, immune, and microbial pathways. Increasing evidence sup ports the gut microbiota’s critical role in modulating brain function and behavior, with implications for various psychiatric and neurodegenerative disorders. This review examines current literature on the mechanistic interplay between gut dysbiosis and mental health, focusing on conditions such as depression, anxiety, Parkinson’s disease (PD), Alzheimer’s disease (AD), schizophrenia, bipolar disorder, and autism spectrum disorder (ASD). The vagus nerve serves as a major conduit for microbial metabolites—such as short-chain fatty acids (SCFAs), tryptophan metabolites, and neurotransmitters—affecting mood, cognition, and neuroinflammation. Immune responses in volving microglia and cytokines (e.g., IL-6, IL-1β) mediate neuroinflammatory cascades via the microbiota–im mune–brain axis. The NLRP3 inflammasome emerges as a central inflammatory mechanism in neurodegeneration. Emerging therapies, including psychobiotics, dietary modifications, prebiotics, probiotics, and fecal microbiota transplantation, show promise but require further validation through robust human trials. Psychotropic medica tions, particularly SSRIs and tricyclics, exhibit antimicrobial activity, potentially inducing dysbiosis and altering gut barrier functions. While animal and in vitro models offer valuable insights, translation to human clinical outcomes remains limited. Despite these challenges, the gut-brain axis represents a promising frontier for novel diagnostic and therapeutic strategies targeting psychiatric and neurodegenerative diseases. Understanding the strain-specific effects, immune-microbiome crosstalk, and microbiota-derived metabolic pathways is critical for personalized medicine approaches.