Gastrointestinal alterations in autism spectrum disorder: What do we know?

There is an emerging body of evidence associating children having autism spectrum disorder (ASD) with gastrointestinal (GI) symptoms, such as abdominal pain, chronic diarrhea, constipation, vomiting, gastroesophageal reflux, intestinal infections, and increased intestinal permeability. Moreover, in many studies, large differences in the composition of intestinal microbiota and metabolic products between ASD patients and controls were reported. Deepening the role and the biology of the gut microbiome may be fundamental to elucidate the onset of GI symptoms in ASD individuals and their etiopathogenetic causes. The gut-brain axis may affect brain development and behaviors through the neuroendocrine, neuroimmune, and autonomic nervous systems.