Gastrointestinal Microbiota Imbalance and Sensory Processing Dysregulation in Autism Spectrum Disorder: A Systematic Review.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by challenges with social communication and repetitive behaviors. Many people with ASD also experience gastrointestinal symptoms and sensory processing dysfunction. New research has identified a potential role for microbial dysbiosis (imbalance of gut microbiota) in these comorbidities. This systematic review aimed to explore the links between gut microbiota composition, gastrointestinal symptoms, sensory processing differences, and dietary patterns in individuals with ASD, as well as the potential for a bidirectional relationship and dietary-based interventions targeting the microbiota. PubMed, Scopus, Web of Science, and Google Scholar were used to retrieve publications from 2011 to 2026, and a systematic review was conducted. Studies were chosen that examined gut microbiota, gastrointestinal symptoms, and sensory processing in people with ASD. Only intervention and observational studies were included. Many people with ASD reported gastrointestinal symptoms, sensory processing differences, restricted dietary patterns, and gut microbiota composition. However, the majority of studies included were cross-sectional, which does not allow for an inference of temporal direction or causality. The evidence indicates there may be a bidirectional relationship between gastrointestinal and sensory symptoms and microbial differences, and the sensory symptoms, food selectivity, food restriction, stool consistency, use of medication, and clinical characteristics may also affect the composition of the microbiota. Initial microbiome interventions had some potential for improvement in selected outcomes, but with limited confidence due to small sample sizes, heterogeneity in methods used, and potential for bias. The current evidence suggests that changes in the gut microbiota composition are associated with gastrointestinal symptoms, sensory dysregulation, and dietary patterns in ASD, but does not provide evidence to indicate that microbial dysbiosis is a primary mechanism. The possibility of reverse causation exists, as the food environment could be influenced by sensory sensitivity and/or eating habits, and, in turn, these factors could affect the composition of the microbiota. To better understand directionality and the efficacy of microbiome-targeted interventions, longitudinal studies and sufficiently powered randomized controlled trials are warranted.