The Gut – Brain Axis in Autism: Pediatric Perspectives

Introduction: Autism spectrum disorder (ASD) is a neurodevelopmental condition frequently associated with gastrointestinal comorbidities such as constipation, diarrhea, abdominal pain, and feeding difficulties. Emerging evidence implicates the gut–brain axis and gut microbiota dysregulation in ASD pathophysiology.Objective: To summarize current evidence on gut microbiota alterations in pediatric ASD, highlighting mechanistic insights, clinical correlations, and potential microbiota-targeted therapies.Methods: A narrative review was conducted of studies published between 2019 and 2025 in PubMed, Scopus, and Web of Science. Included studies focused on pediatric populations (0–18 years) reporting gut microbiota composition, metabolite profiles, or interventions targeting the microbiota in ASD. Non-original research, animal studies, and studies without relevant outcomes were excluded.Results: Children with ASD exhibit gut dysbiosis, characterized by increased Firmicutes and Pseudomonadota (formerly Proteobacteria), decreased Bacteroidetes, and a reduced Bacteroidetes-to-Firmicutes ratio. These microbial shifts correlate with gastrointestinal and behavioral manifestations and are associated with intestinal barrier dysfunction, immune activation, and altered short-chain fatty acid (SCFA) profiles—specifically elevated propionate and reduced butyrate—potentially contributing to neuroinflammation, neurotransmitter imbalance, and synaptic dysfunction. Microbiota-targeted interventions, including probiotics, prebiotics, dietary modifications, and fecal microbiota transplantation, show potential benefits in improving gastrointestinal symptoms and, in some studies, behavioral outcomes. However, methodological heterogeneity, small sample sizes, and interindividual variability limit the generalizability of findings.Conclusions: Gut dysbiosis appears to play a significant role in the pathogenesis and clinical heterogeneity of pediatric ASD. Future research with standardized methodologies, validated biomarkers, and precision medicine approaches is essential to develop individualized therapeutic strategies and optimize long-term outcomes.