Early Gut Microbiota and Neurodevelopmental Trajectories: Implications for Pediatric Neuropsychiatric Vulnerability—A Narrative Review

Neurodevelopment is a dynamic and multifactorial process, critical in the early stages of life, involving the formation of neural networks, the establishment of synapses, and the maturation of cognitive, social and emotional circuits. In this context, the gut microbiome emerges as an essential regulator of neurodevelopment, exerting influences through multiple biochemical and immunological mechanisms that define the “gut-brain axis”. The microbiota modulates neurodevelopment by regulating neurotransmitters (serotonin, dopamine, GABA), the production of microbial metabolites, including short-chain fatty acids, the modulation of inflammatory cytokines, and vagal signaling to the central nervous system. Recent evidence highlights the role of microbiota in modulating microglia, synaptogenesis, dendritic maturation, and neuronal plasticity, emphasizing how these processes are influenced by microbial activity rather than providing a comprehensive treatise on plasticity itself. Gut microbiota disturbances, or dysbiosis, have been associated with various neuropsychiatric and neurodevelopmental disorders, contributing to cognitive, behavioral, and emotional dysfunctions. This article summarizes, in a narrative manner, the main dysbiosis patterns identified in these disorders and the biological mechanisms by which the microbiome influences neuronal development and function, including immune–neuronal interactions, metabolomic modulation, and neuroendocrine signaling. Finally, emerging directions of intervention aimed at adjusting the microbial profile, such as dietary adjustment, the use of probiotics, prebiotics, symbiotics, and fecal microbiota transplantation, are presented with the aim of positively influencing neurodevelopment and preventing or ameliorating associated dysfunctions. This review emphasizes the need for longitudinal, rigorous, and controlled clinical trials to validate the efficacy of microbiota modulation strategies and to substantiate their integration into individualized pediatric management protocols.