Microbial metabolites at the nexus of gut-brain communication and neurodevelopmental disorders.

The microbiota-gut-brain axis (MGBA) has emerged as a critical regulator of neurodevelopment, with microbial metabolites serving as key signaling molecules that bridge the intestinal ecosystem and the central nervous system. This review gathers current evidence that connects disruptions in microbial metabolites to the pathogenesis of neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Our comprehensive overview discusses major neuroactive metabolite classes-short-chain fatty acids (SCFAs), tryptophan derivatives, bile acids, and phenolic compounds-and their established roles functions in affecting neuroinflammation, epigenetic programming, synaptic function, and blood-brain barrier integrity. Converging evidence from human multi-omics studies and preclinical models frequently reported patterns of metabolic dysregulation in NDDs, including reduced SCFA production, altered kynurenine pathway metabolites, and accumulation of neurotoxic compounds such as para-cresol (p-cresol). However, substantial heterogeneity exists across studies, and causal evidence in humans remains predominantly associative. We further examine the critical early-life window during which the metabolite-producing microbiome is shaped by maternal factors, nutrition, and environmental exposures, with lasting consequences for neurodevelopmental trajectories. Finally, we discuss new intervention strategies such as probiotics, dietary substrates, fecal microbiota transplantation, and metabolite-based therapies, and propose a plan to transition from associative findings to causal, personalized approaches using microbial metabolites as biomarkers and therapeutic targets in child neurodevelopment.