Children with autism spectrum disorder (ASD) appear to be two-and-a-half times more likely to have persistent gastrointestinal (GI) symptoms than those with normal development.

The findings were based on a considerably large longitudinal study who reported their children's GI symptoms during the first three years of life, Columbia University's Mailman School of Public Health reported.

The results showed the mothers of children with ASD were more likely to report that their children experienced constipation and food intolerance between the ages of 6 and 18 months; these children also had higher reported rates of  diarrhea, constipation, and food intolerance in between the ages of 18 and 36 months when compared with children of typical development.

"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, PhD, first author and assistant professor of Epidemiology at the Mailman School.

The researchers noted that while higher levels of GI symptoms appear to be associated with autism, but these symptoms do not indicate that a child is more likely to develop ASD and all people with autism do not struggle with GI problems.

A study prompted by a recent case of an autistic child showing significant symptoms improvement following a course of antibiotics also suggests a link between the condition and gut bacteria.

"Delineating factors that disrupt signaling along the gut-brain axis while the brain is still under development may ultimately provide a key to understanding how the disorder occurs in the subset of children with autism and GI complaints," said W. Ian Lipkin, the study's senior author, and John Snow professor of Epidemiology and director of the Center for Infection and Immunity at the Mailman School.

The findings were published in a recent edition of the journal JAMA Psychiatry.