Probing the link between autism, GI disorders and the microbiome

autism microbiome
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Sonia A. Ballal is an attending physician in the Division of Gastroenterology, Hepatology and Nutrition at Boston Children’s Hospital.

Eleven-year-old Lyle has autism and doesn’t speak, but his mother is used to reading his nonverbal cues. He prefers a routine, but has always been a generally cheerful child who enjoys school and playing with his little sister.

Several weeks before I met Lyle (not his real name), his mother observed a dramatic shift. He was agitated, at times hitting his head against the wall, not receiving his typical sunny reports from school. As his mother told Sarah Spence, MD, PhD, his primary neurologist at Boston Children’s Hospital, even his toilet training seemed to be regressing, with Lyle bringing a diaper to his mother multiple times daily in order to have a large, sometimes mucus-coated stool.

Ballal_Sonia resizedAs Lyle’s gastroenterologist, my focus was on this last symptom. Stool studies revealed Giardia, a parasitic infection commonly found in day care settings.

Are children with autism spectrum disorder (ASD) more prone to GI problems? Consistent with the reports of many parents, multiple studies have suggested an increased prevalence of GI concerns in children with ASD. A 2014 meta-analysis reviewed 14 of these studies and concluded that a child with ASD is four times more likely than a child without ASD to have a GI concern.

Clinicians often chalk up these GI problems to behavioral etiologies: limited diets, difficulty with change, certain repetitive behaviors, obstacles with communication. These are all autistic behaviors that could predispose children to constipation, obesity, diarrhea, feeding difficulties and many other GI problems.

But is there more to the story? Over the last 20 years, the medical and lay press has been filled with debates over theories such as a “leaky gut” in ASD – the idea that abnormally permeable intestines are allowing substances to leak into the bloodstream and harm the brain. (Sometimes this idea has been connected to the now-strongly refuted link between vaccines and autism).

An IBD – ASD link

Preclinical and clinical studies are inconclusive about leaky gut as a clinical entity. But interestingly, recent large-scale studies that surveyed electronic health records have found an increase in inflammation-based diseases, such as inflammatory bowel disease (IBD), in both adults and children with ASD. In children 17 and under, IBD was twice as likely to be present in those diagnosed with ASD.

brain gut connection autism IBD ASDWhile the research team called the study “exploratory and suggestive,” an in-depth investigation in 2015 concluded that the age-adjusted prevalence of IBD among patients with ASD was indeed higher than that in control groups and higher than nationally reported rates of pediatric IBD. Combined with others, these studies suggest that autistic behaviors alone may not explain the increased GI problems in children with ASD.

Studying the microbiome in autism

Increasing evidence suggests that the bacteria, viruses and fungi that inhabit our GI tracts — collectively termed the microbiota — may be part of the equation. Research using mouse models of autism shows perturbations in the gut bacteria of mice with ASD-like features as compared with controls. Restoring a microbiota more closely resembling the controls’ did lead to a decrease of the ASD-like features observed in these mice. This suggests that the type of bacteria in the mouse gut may have an influence on neurodevelopmental behavior.

Could changes in the gut microbiota help us understand the association between ASD and GI problems? Do relationships seen in mice hold in humans? To find out, Scott Snapper, MD, PhD, Athos Bousvaros, MD, MPH, and I are currently recruiting individuals under 30 years old with diagnoses of both ASD and IBD. Our goal is to better characterize this unique population of patients clinically and to compare their gut microbiomes with those of patients with IBD alone and ASD alone.

microbiome autism
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Potentially, this study may offer some insight into why people with ASD have a higher incidence of GI problems, specifically IBD. Meanwhile, as gastroenterologists, we have begun working closely with colleagues in the Autism Spectrum Center to provide timely evaluations for children with Gl concerns. Elana Bern, MD, MPH and Nancy Sullivan, PhD, with others in the Growth and Nutrition Program, evaluate and treat patients with ASD and feeding difficulties, while Lynn Tougas and other dieticians carefully mine nutritional histories and offer guidelines for a balanced intake.

My patient Lyle began an antibiotic course, together with a probiotic to maintain a proper balance of bacteria in his GI tract. Within three days, his stools decreased to once daily or every other day. His self-injurious behavior diminished, and he returned to playing with his sister.

While behavioral symptoms don’t always resolve when GI symptoms are treated, resolving the source of a child’s pain and discomfort can positively impact behavior. The data suggest that a GI physician can be — and arguably, should be — an important part of the care team for children with ASD.

For more information about the ASD microbiome study or for an appointment in Gastroenterology/Nutrition, phone 888-920-6597.