Gut Microbiota and Autism Spectrum Disorder: Current Evidence, Mechanisms, and Therapeutic Potential

Abstract

Autism spectrum disorder (ASD) is a neurodevelopmental condition frequently associated with gastrointestinal (GI) dysfunction and altered gut microbiota. Increasing evidence suggests that the microbiota–gut–brain (MGB) axis may contribute to ASD through interactions involving neural, immune, endocrine, and metabolic pathways. This narrative review aimed to summarize current evidence regarding gut microbiota alterations in ASD, proposed MGB mechanisms, and the therapeutic potential of microbiome-based interventions. A structured literature search was conducted using PubMed, Scopus, and Google Scholar for studies published between 2019 and 2025, and 14 core articles were selected for thematic synthesis. Current evidence indicates that individuals with ASD commonly exhibit gut dysbiosis, including altered abundance of taxa such as Proteobacteria, Actinobacteria, Sutterella, Clostridium, and Bifidobacterium. However, findings remain heterogeneous, and no consistent ASD-specific microbial signature has been identified. Proposed mechanisms linking dysbiosis to ASD include altered intestinal permeability, inflammatory cytokine signaling, short-chain fatty acid imbalance, and microbial metabolite dysregulation. Nevertheless, much of the mechanistic evidence derives from animal and experimental studies, while human evidence remains largely associative. Microbiome-based interventions, including probiotics, dietary modification, prebiotics, synbiotics, and fecal microbiota transplantation (FMT), show potential benefits, particularly for GI symptoms. However, current evidence is limited by small sample sizes, methodological heterogeneity, and insufficient long-term safety data. Overall, the gut microbiome appears to function as a biologically relevant modifier of ASD phenotype and symptom severity rather than a definitive causal factor. Future research should prioritize longitudinal human studies, patient stratification, multi-omics integration, and rigorous randomized controlled trials to improve mechanistic understanding and therapeutic translation.