Children with autism are more likely to have symptoms of irritable bowel syndrome than kids without ASD.

Autism spectrum disorder (ASD) is usually defined by its social and behavioral symptoms, and complaints of stomach problems among children with ASD are sometimes written off as just stories.

But a new study, appearing in the journal Pediatrics, is the first of its kind to analyze all the published, peer-reviewed research about gastrointestinal (GI) problems in children with ASD. It shows that autistic children do in fact experience more (and more severe) stomach problems than other children their age.

Researchers from the Marcus Autism Center, Children’s Healthcare of Atlanta, and Emory University’s School of Medicine found that these GI symptoms are real and detrimental to children. The study revealed that children with ASD are more likely to have constipation and diarrhea, and to complain about abdominal pain.

Researchers don’t know why autistic children are more likely to have stomach problems, but picky eating and other dietary restrictions characteristic of some children with ASD seem to play a role in their GI troubles.

“Children with ASD are known to experience feeding problems and related dietary issues,” explained William Sharp, Ph.D., director of the Pediatric Feeding Disorders Program at Marcus Autism Center and an assistant professor of autism and related disorders at Emory University. “These concerns most often involve strong preferences for fats, snacks, and processed food, and rejection of fruits and vegetables. This pattern of food selectivity may lead to or make worse GI symptoms, such as abdominal pain or constipation.”

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Over the long-term, these GI symptoms can be damaging. Dr. Barbara McElhanon, a pediatric gastroenterologist at Children’s Healthcare of Atlanta and an assistant professor of pediatrics at Emory University, says that accidents, even by toilet-trained children, are one possible consequence. Children with gastroesophageal reflux disease (GERD) are also at an increased risk for esophageal cancer if the condition is left untreated.

Effective communication is challenging for any child, but it can be especially difficult for children with autism to express themselves.

And, as the findings suggest, some of their behavioral symptoms may actually stem from gastrointestinal problems. The discomfort and pain of GI issues like constipation and diarrhea can lead to what appears to be disruptive behavior.

Several issues have kept the connection between ASD and GI disorders from receiving the attention and study it deserves—and one myth has been particularly damaging.

“The unfounded assertion that vaccinations somehow caused an inflammatory GI disease which then caused autism has significantly hindered progress in this field for years,” Sharp said. “That controversy diverted attention from the GI needs of children with ASD, and we hope that our work helps spur renewed investment for addressing these needs.”

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Children’s GI complaints need to be taken seriously, and communication between doctors and parents is key, especially for those children who struggle to speak for themselves.

McElhanon recommends that doctors ask parents of children with ASD specifically about their GI functions and symptoms.

“They should be asking the families for information about the [characteristics of the child’s] stool as well as behaviors, like increased irritability, before using the toilet,” McElhanon said. “Similarly, questions about behaviors during eating and with specific foods may uncover concerns for the doctors. Open-ended questions such as, ‘Do you have concerns that your child’s stomach hurts?’ are also helpful.”

Parents should record their child’s habits and report any issues to their pediatricians.

“I would urge parents to write down the complaints, making sure to include the child’s diet, bowel movements, and behaviors,” McElhanon said. “A pattern may be found that can help the pediatrician, gastroenterologist, or nutritionist pinpoint a potential problem.”