FRIDAY, Jan. 20, 2017 (HealthDay News) -- Many children with autism suffer from gastrointestinal problems, such as belly pain and constipation. And new research suggests that these issues may stem from a heightened response to stress.

"When treating a patient with autism who has constipation and other lower gastrointestinal issues, physicians may give them a laxative to address these issues," said study author Dr. David Beversdorf.

"Our findings suggest there may be a subset of patients for which there may be other contributing factors. More research is needed, but anxiety and stress reactivity may be an important factor when treating these patients," he added.

Beversdorf is an associate professor at the University of Missouri-Columbia's Thompson Center for Autism and Neurodevelopmental Disorders.

The new study included 120 young people with autism and their parents. The parents provided information about their children's gastrointestinal symptoms. Overall, 51 of the children had these issues and 69 didn't.

The children underwent a 30-second stress test. To evaluate their response to the stress, the researchers collected saliva samples from each participant before and after the test to measure the children's cortisol levels.

Cortisol is a hormone the body releases in times of stress. The body releases cortisol to help prevent inflammation caused by substances called cytokines that are linked with autism, stress and gastrointestinal issues, the researchers said.

The study showed that the children with gastrointestinal symptoms had higher cortisol levels in response to the stress test than those who didn't have these symptoms.

"We know that it is common for individuals with autism to have a more intense reaction to stress, and some of these patients seem to experience frequent constipation, abdominal pain or other gastrointestinal issues," Beversdorf said in a university news release.

"To better understand why, we looked for a relationship between gastrointestinal symptoms and the immune markers responsible for stress response," Beversdorf explained. "We found a relationship between increased cortisol response to stress and these symptoms."

The study was published recently in the journal Brain, Behavior, and Immunity.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about autism.