July 27, 2009 -- For years, a suspected link between gastrointestinal problems and autism has been debated, with medical reports describing GI symptoms in up to 84% of children with the developmental disorder.
The debated link has limited epidemiologic evidence but popular widespread acceptance, leading to the practice of placing some children with autism on restrictive diets.
Now, a new study from Mayo Clinic in Rochester, Minn., has found no apparent overall link between GI disorders and autism, although the researcher did find some individual GI problems are more common in children with autism.
''Nobody has done a population-based study to see if there is a difference in incidence of GI symptoms [in children with and without autism]," says Samar H. Ibrahim, MCChB, a pediatric fellow in gastroenterology and an instructor of pediatrics at the Mayo Clinic.
So Ibrahim and her colleagues did so.
GI Disorders &amp; Autism Link Study: Details
She compared 121 children with the disorder to a control group of 242 age-matched children without a diagnosis of autism, following them for a median (half longer, half less) of about 18 years. The children were all residents of Olmstead County, Minn.
Autism is typically seen in the first three years of a child's life, marked by difficulty in social interaction and communication, late talking, and restrictive or ritualistic behaviors.
"We compared the incidence of GI disorders in patients vs. controls," Ibrahim tells WebMD. She looked for specific GI diagnoses made before age 21, grouping them into five categories:
- Abdominal bloating, discomfort, or irritability
- Gastroesophageal reflux (acid reflux) or vomiting
- Feeding issues or food selectivity
"We did find that the overall incidence of GI symptoms was not different between the two groups," she says. But she did find that two specific problems -- constipation and feeding issues -- were more common in the children with autism.
Twice the proportion of children with autism had constipation than did the control group -- 33.9% vs. 17.6%. Although 24.5% of children with autism had feeding issues or food selectivity issues -- such as a feeding problem, lactose intolerance, loss of weight, or loss of appetite -- just 16.1% of the children without autism did.
In the study, the researchers found few children with autism with specific GI disease diagnoses, she says, although both groups had "nonspecific GI symptoms, such as complaints of abdominal pain. The frequency of GI symptoms among children with autism was about 77%, and 72% in those without it.
GI Disorders &amp; Autism Link: Interpretations
Explanations other than a GI disease probably explain the two GI symptoms found to be more common in the children with autism, Ibrahim tells WebMD.
Children with autism often show ritualistic tendencies and a need for routine, such as sameness in the diet. They may not drink enough water or take in enough fiber, practices that can lead to constipation and the feeding issues, she says.
"Some are on medications that slow down the gut," she says, and that could also contribute to constipation problems. Her conclusion: subgroups of children may have GI problems that may be the result of their behavioral characteristics.
She cautions that children with autism shouldn't be treated with restrictive diets until there is evidence of a GI disorder.
In an interview with WebMD, Mark A. Gilger, MD, a gastroenterologist at Baylor University who wrote an accompanying editorial, says, ''There have been questions surrounding the gut and autism for many, many years."
The Mayo research team, he says, "were probably trying to put the story to rest. What they found is they couldn't fully put it to rest. They raise the spectrum there could be subtypes in which there could be something going on [with the gut]."
Among other suggestions, some experts have proposed that a GI abnormality leads to both intestinal inflammation and neuropsychiatric dysfunction.
More recently, Gilger writes, Vanderbilt University researchers reported that disrupted signaling involving a protein called MET, which is involved in brain development, gut repair, and other functions in the body, ''may contribute to the risk for autism spectrum disorder that includes familial gastrointestinal dysfunction."
More research is needed, Gilger says, especially leads about genetic links such as the Vanderbilt research.
GI Disorders &amp; Autism Link: Second Opinion
''The study is important but not definitive," says Geraldine Dawson, PhD, chief science officer for Autism Speaks, an advocacy group.
"It's very possible there are subgroups of kids [with autism] where part of their symptoms involve the GI tract."
She says the study points to the need for more study -- and to the need to not chalk up all behavior changes to the autism.