Researchers in Sweden have found no connection between celiac disease in autism in a large population study.

Interest in gluten-free diets has grown recently, as parents search for alternative ways to relieve symptoms of autism in their children. However, there’s little evidence that this naturally occurring food compound can trigger autism or make it worse.

A large study led by Swedish researchers adds some clarity to the issue, finding no connection between autism spectrum disorder (ASD) and celiac disease (CD). The role of gluten and gluten-free diets in autism, however, is still unclear.

Celiac disease is an immune condition triggered when people who are allergic to gluten eat foods containing wheat, rye, or barley. The small intestine becomes inflamed, and gluten can damage the intestine’s protective lining.

Recognizing Gluten Allergy Symptoms

Previous studies have linked celiac disease to other neurological conditions in children, such as headaches, numbness or tingling in the hands and feet, and nerve damage. It’s role in autism, however, is up for debate.

In the current study, published today in JAMA Psychiatry, researchers reviewed the medical records and some biopsy results of more than 40,000 people from Sweden.

The bulk of these patients were diagnosed with celiac disease. The rest had related, but less severe levels of gluten intolerance, or had tested positive for celiac disease antibodies. These patients were compared to more than 200,000 people of similar sex and age who had no history of celiac disease.

After analyzing the data, the researchers found no link between patients who had previously been diagnosed with autism and celiac disease. In addition, there was no association between autism and less severe gluten sensitivity.

“I agree with part of the authors conclusion that they found very weak evidence of any association of ASD and CD,” says Robert Nickel, M.D., a developmental pediatrician at Oregon Health and Science University, who was not involved in the study.

However, the researchers did find a four-fold increase in the rate of autism among people who had a normal intestinal lining but a positive celiac antibody blood test.

This may indicate that people in the study who were diagnosed with autism and tested positive for celiac antibodies are more sensitive to gluten, even though they don’t have full-blown celiac disease. The design of the study, though, didn’t allow the researchers to say that being gluten sensitive caused autism, or the other way around.

The positive antibody test could also be part of an overall increase in food sensitivities in the population.

“The authors suggest, perhaps correctly, that the positive [antibody] tests in individuals with normal [intestinal] biopsies may relate to a broad pattern of sensitization,” says Nickel.

Autism is a complex developmental disorder that leads to difficulty with communication and social interaction, as well as repetitive behaviors. According to the Centers for Disease Control and Prevention, about 1 in 88 children have been diagnosed with autism spectrum disorder.

The exact cause of autism is unknown, and there is currently no cure. This has led many concerned parents to try restrictive diets, such as those that exclude gluten and the milk-protein casein. Research on these types of diets, however, is still ongoing.

While the new study found no link between autism and celiac disease, it did little to address the role of diet in improving the symptoms of autism.

“The study certainly doesn’t clarify the current discussion of gluten and gluten-free diets and autism,” says Nickel.