Exploring the Gut-Brain Axis in Autism Spectrum Disorder: A Cross-Sectional Correlational Study of Microbiome Diversity and Neurobehavioral Severity in Children
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Background: Autism Spectrum Disorder is a heterogeneous neurodevelopmental condition frequently accompanied by gastrointestinal symptoms and altered dietary patterns. Emerging evidence suggests that gut microbial imbalance may influence neurobehavioral expression through the microbiota–gut–brain axis, but data from Pakistan remain limited. Objective: To examine the association between gut microbiota diversity, selected bacterial genera, gastrointestinal symptom burden, and behavioral severity among children with Autism Spectrum Disorder attending a tertiary care hospital in Punjab, Pakistan. Methods: This cross-sectional correlational study included 100 children aged 3–12 years with clinically confirmed Autism Spectrum Disorder recruited through consecutive sampling. Demographic and clinical data were collected using a structured proforma, behavioral severity was assessed using a standardized autism severity rating tool, gastrointestinal symptoms were recorded through parent report, and stool samples were analyzed using 16S rRNA-based microbiome profiling. Alpha diversity, observed species richness, and relative abundance of selected bacterial genera were examined in relation to behavioral and gastrointestinal variables. Results: The mean age was 7.2 ± 2.4 years, and 72% were male. Gastrointestinal symptoms were present in 68% of children. Mean Shannon diversity declined from 4.2 ± 0.5 in mild ASD to 3.1 ± 0.7 in severe ASD. Shannon diversity was negatively correlated with total behavioral severity score (r = −0.41, p = 0.001) and gastrointestinal symptom burden (r = −0.39, p = 0.002). Children with gastrointestinal symptoms had lower microbial diversity and higher behavioral severity than those without gastrointestinal symptoms. Conclusion: Reduced gut microbial diversity and altered bacterial composition were associated with greater behavioral severity and gastrointestinal symptom burden in children with Autism Spectrum Disorder. These findings support the clinical relevance of the microbiota–gut–brain axis but require confirmation through longitudinal multicenter studies.
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