Children of mothers who have autoimmune diseases, such as rheumatoid arthritis, celiac disease or type 1 diabetes, are at greater risk of having autism, a new study shows.

The study, published online in the journal Pediatrics, looked at more than 689,196 children born in Denmark between 1993 and 2003.  Scientists found 3,325 of these children were diagnosed with autism spectrum disorders and discovered that many also had a family history of autoimmune diseases.

Autoimmune diseases develop when the body fails to recognize its own organs and tissues, attacking them as it would a dangerous invader.

In this study, for the first time, researchers discovered an increased risk of autism in children with a maternal history of celiac disease - a condition where people can’t digest gluten, a protein found in wheat, rye and barley. Researchers also confirmed previous studies that found an increased risk of autism in children whose moms had rheumatoid arthritis or type 1 diabetes.

Children of mothers with celiac disease had a 197 percent increased risk of autism, while children of mothers with rheumatoid arthritis had a 56 percent increased risk. Those with moms who had type 1 diabetes had a 114 percent increased risk.

They also found a 78 percent increased risk of autism if the father had type 1 diabetes, but not if the father had arthritis or celiac disease.

Researchers say their results suggest a complex association between family history of certain autoimmune diseases and autism.

“A common genetic background could explain the results for diabetes, while for arthritis it is more possible it is caused by immune responses in the mother or factors in the fetal environment,” says Hjördis Osk Atladottir, MD the lead author of the study done at the University of Aarhus in Aarhus, Denmark.

“We can’t conclude anything based on only our results but our results are a part of a bigger puzzle of many studies, suggesting that autism and the immune system, and autoimmunity in particular, are connected,” he adds.

The researchers also stress that current or future parents with an autoimmune diseases shouldn’t worry too much about the study results because the large majority of people affected by these conditions do not have children with autism.

Paul Ashwood, PhD, is an immunologist at the University of California, Davis M.I.N.D. Institute in Sacramento who specializes in studying the role of the immune system in autism. He says this is an interesting and large study that supports existing research that shows autism often runs in families.

“It’s an interesting study and its sort of a study that confirms some previous observations that maybe a family history of autoimmune diseases could be associated with the autism spectrum disorder,” Ashwood says.

Ashwood points out that this study only looked for associations between diseases. That means it doesn’t prove that autoimmune disorders cause autism. And it doesn’t mean this is the case for all children with autism. But he says it’s helpful because it adds to the existing body of research. 

“If you take all these studies as a whole, it suggests that an immune dysfunction or something going wrong with the immune system during pregnancy in the mothers could be associated with a child with autism spectrum disorder.”

“But at the moment, for the majority of cases of children with autism, we don’t know what the cause is,” he says. So, “I think it’s helpful in that it’s revealing some clues as to some potential factors that may be important in a risk for having a child with autism.”

Next, Danish researchers say they are going to look at the connection between autism and other forms of immune stimulation, such as maternal infection, during pregnancy.