According to a new study at the University of California in the US common gastrointestinal (GI) symptoms such as diarrhea constipation and bloating are linked to troubling sleep problems self-harm and physical complaints in pre-school children especially those with autism. According to the new study published in the journal Autism Research these GI symptoms are much more common and potentially disruptive in young kids with autism. Researchers say that this study highlights the link between GI symptoms and some problematic behaviours we see in preschool-aged children. Gastrointestinal concerns are frequently reported by parents of children with autism spectrum disorder (ASD).