Gastrointestinal distress and gut microbial imbalances are commonly found in children with autism spectrum disorder, and therefore may play a key role in the development of the disorder. This scoping review aimed to examine the extent, range and nature of research conducted in the past 6 years that focused on furthering our understanding of autism spectrum disorder and its association with gut microbiota. A literature review was performed with predetermined key words. Studies were screened and selected based on defined inclusion and exclusion criteria. A total of 19 studies were included for final analysis. While there are continuous reports of differences in gut microbiota between autism spectrum disorder and neurotypical individuals, knowledge about the consistency in the presence and abundance of bacterial species, as well as metabolites, remains deficient. Treatments such as special diets, vitamin, prebiotic, probiotic, and microbiota transfer therapy show promising therapeutic potential, yet are in their infancy of investigation. Overall, further research with rigorous methodologies is required to support and strengthen the reliability of existing findings. Future research should aim to increase sample sizes, eliminate biases, and subgroup autism spectrum disorder groups to help accommodate for inter-individual variation. As increasing evidence of a unique autism spectrum disorder microbiome and metabolome is acquired, autism spectrum disorder-specific biomarkers can be identified. These biomarkers have great implications in terms of elucidating the molecular mechanisms of autism spectrum disorder, preventing the onset of autism spectrum disorder, and improving treatments for individuals with autism spectrum disorder.
Keywords: autism spectrum disorder; autism spectrum disorder behavior; gastrointestinal disorders; gut microbiota; microbiota–gut–brain axis.