Probiotics and Prebiotics in the Treatment of Autism Spectrum Disorder: A Narrative Review.

More than half of the patients with autism spectrum disorder (ASD) have gastrointestinal (GI) comorbidities, such as constipation, indigestion, abdominal pain, and diarrhea. Recent studies suggest prescribing probiotics and prebiotics in ASD could relieve GI disturbances and behavioral issues. This narrative review generalizes the research progress on probiotic and prebiotic therapies for ASD over the past 5 years and further discusses the underlying mechanisms of interaction between probiotics and prebiotics with ASD. Preliminary evidence has demonstrated the beneficial effects of probiotics and prebiotics on GI problems, autism-related behavioral disorders, and gut microbiome composition; the mechanism of probiotics and prebiotics in the treatment of ASD is mediated through inflammatory signaling pathways, metabolic pathways, neuronal signaling pathways, and the involvement of the vagus nerve. However, the results are inconclusive and mainly generated by animal experiments. Overall, the present review recommends further standardization of clinical studies to draw more robust evidence for prescribing probiotics and prebiotics in ASD.