Autism and gastrointestinal bacteria connection

Autism spectrum disorders (ASD) are neurodevelopmental disorders,  characterized by difficulties in social interactions, verbal and non-verbal communication, and stereotypic or repetitive behaviors.  Gastrointestinal (GI) distress is common in children with ASD and include,  abdominal pain, bloating, diarrhea and constipation. The high frequencies of these GI symptoms could be due to abnormal GI bacterial flora in individuals with ASD. The GI bacterial flora  are important for nutrition and metabolic processes and growing evidence suggest that they play a role in brain development, behavior, and gene expression via neural, endocrine, and immune pathways. Emerging research on the gut-microbiome-brain connection in both mice and humans has shed new light on the pathogenesis of various neurological diseases including ASD.

A total of 15 cross-sectional studies, with a combined sample of 562 individuals reported significant differences in the prevalence of GI bacteria between ASD children and controls, in some bacteria in the Firmicutes  (including Clostridium spp. ), Bacteroidetes  and Proteobacteria phyla. The level of the probiotic Bifidobacterium  spp. was lower in children with ASD than in controls. Some studies found an association between the severity of GI symptoms and the severity of autism.

Future research should explore whether administration of probiotic bacteria, and or antimicrobials could restore normal gut microbiota, reduce inflammation, restore epithelial barrier function, and potentially ameliorate behavioral symptoms associated with some children with ASD.