Data Cast Doubt on Relationship Between Autism, GI Illness

Autism and gastrointestinal (GI) disease are linked, some people suggest.

So Samar Ibrahim, M.D., a pediatric gastroenterology fellow at the Mayo Clinic in Rochester, Minn., and colleagues undertook a large population-based study to try to clarify this issue.

They examined nonspecific GI symptoms as well as specific diagnoses of GI diseases in 124 children with autism and in 248 control children from birth to age 21. Nearly all of the youngsters had received their medical care at the Mayo Clinic throughout the years studied; hence detailed, computerized records of their GI symptoms and diagnoses were available for analysis. Ibrahim and his team then compared the GI symptoms and diagnoses of the autism group with those of the control one.

“The biggest finding,” Ibrahim told Psychiatric News,“ was that there was no significant difference in the overall incidence of gastrointestinal symptoms between subjects with autism and normal control subjects....” However, the incidence of symptoms in both groups was high. By age 20, 77 percent of the autism subjects and 72 percent of the control ones had had at least one GI symptom recorded in their medical files.

Nonetheless, the study did find that the incidence of two GI symptoms—feeding difficulties and constipation—was significantly greater in the autism subjects.

As for specific diagnoses of GI diseases, very few in either the autism group or the control group received them. One autism subject had Crohn's disease, another intestinal disaccharidase deficiency, and a third pancreatitis. One control subject had a milk allergy, two had lactose intolerance, and one had pancreatitis. No one in either the autism group or the control group had been diagnosed with celiac disease.

So what should clinicians or parents of autistic children make of these findings, which appeared in the August Pediatrics? “Many children with autism are treated with restrictive diets; vitamin, mineral, and other dietary supplements; as well as various medications aimed at putative gastrointestinal disorders,” Ibrahim and his group wrote. “The findings from our study suggest that such treatments should not be provided indiscriminately to children with autism unless there is explicit evidence indicating the presence of a gastrointestinal disorder in a specific case.”

Regarding feeding difficulties and constipation, the researchers believe that they are due to autistic children's behaviors, not to autism's causing some underlying organic gastrointestinal disease.

“The ritualistic tendencies, need for routine, and insistence on sameness that are characteristic of children with autism may lead these children to choose and demand stereotyped diets that may result in an inadequate intake of fiber, fluids, and other food constituents,” the researchers suggested.

In an accompanying editorial, Mark Gilger, M.D., and Carol Anne Redel, M.D., pediatric gastroenterologists at Baylor College of Medicine in Houston, complimented the study on being “well performed.” But more research is still needed, they wrote. For instance, it may be possible that in some cases autism-spectrum disorders are linked to specific GI problems, they indicated.

One possibility, they suggested, is Rett syndrome. “Girls with Rett syndrome manifest clear gastrointestinal abnormalities such as gastroesophageal reflux and possibly esophageal dysmotility.”

Still another possibility, they pointed out, is that certain genetic abnormalities might underlie both an autism-spectrum disorder and GI problems. Indeed, a growth factor receptor called Met receptor tyrosine kinase is known to function in both brain development and GI repair. A variant in the gene that makes the receptor has been linked with autism. Thus, it is conceivable that this gene variant might contribute to both autism and GI problems, they speculated.

The study was funded by the David and Elaine Dana family and the National Institutes of Health.

An abstract of “Incidence of Gastrointestinal Symptoms in Children With Autism: A Population-Based Study” is posted at<http://pediatrics.aappublications.org/cgi/content/abstract/124/2/680>.▪