Gastrointestinal issues common among many on the spectrum are often apparent in infancy — well before individuals are diagnosed with the developmental disorder, researchers say.

Children with autism are more than twice as likely as typically-developing kids to have regular gastrointestinal symptoms as infants and toddlers, according to findings published this week in the journal JAMA Psychiatry.

For the study, researchers used information collected on over 45,000 children in Norway. The data included responses to questionnaires mothers completed about their children at ages 18 and 36 months.

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Nearly 200 of the kids studied were diagnosed with autism by the time they turned 3. Mothers of these children were more likely to have reported that their child experienced constipation and food allergy or intolerance between the ages of 6 and 18 months. They also reported more instances of diarrhea, constipation and food allergy or intolerance between 18 and 36 months than did parents of typically-developing kids.

What’s more, childrenĀ later diagnosed with autism were more likely than those with other developmental delays to have experienced gastrointestinal issues when they were little, the study found.

“We not only learned that these symptoms appeared early in infancy; we also found that children with ASD were at significantly increased risk for these symptoms to persist compared with typically-developing children,” said Michaeline Bresnahan of Columbia University who led the study.

Though stomach issues often resolved themselves in typically-developing children by age 3, the problems more frequently remained in kids with autism, researchers said.

Nonetheless, they caution that despite the association between autism and gut troubles, most children with gastrointestinal problems do not develop autism nor does everyone on the spectrum experience such symptoms.

“GI symptoms alone need not be cause for alarm,” Bresnahan said.