There's no link between celiac disease and autism spectrum disorders, a nationwide study from Sweden says.
People who were diagnosed with an autism spectrum disorder (ASD) in the study were no more likely to be diagnosed with celiac disease than people without an ASD.
Dr. Jonas Ludvigsson, the study's lead author, said the finding offers one less thing to worry about for people with either celiac or ASDs.
"To them, this is good news," Ludvigsson, of Sweden's Karolinska Institute, said.
Some researchers have reported on single cases of people who were diagnosed with an ASD and who were then diagnosed with celiac disease.
In celiac disease, which is estimated to affect about one percent of Americans, an individual's own immune system attacks the small intestines if they eat gluten, a protein in wheat and certain other grains.
Other studies have found that switching those people to gluten-free diets appeared to also reduce ASD symptoms, but larger trials have not shown any link between the two conditions.
For the new study Ludvigsson and his colleagues connected several Swedish databases to compare the celiac disease diagnoses among people with ASDs to a group of people without the developmental disorders.
The researchers had information on more than 250,000 people and they found no difference in the rate of ASD diagnoses among people with celiac disease compared to those without the condition.
About 44 people per 100,000 were diagnosed with an ASD before they were diagnosed with celiac disease. That compared to about 48 people per 100,000 who were diagnosed with an ASD but not with celiac disease.
There was, however, a link between ASDs and a positive blood test for celiac disease, which alone is not enough to diagnose someone with the condition. A celiac disease diagnosis requires both a positive blood test and evidence of damage to the small intestine.
"It's very interesting in my mind, because it points to some relationship to gluten that's separate from celiac disease," Dr. Peter Green, professor of medicine and director of the Celiac Disease Center at Columbia University Medical Center and a gastroenterologist at NewYork-Presbyterian/Columbia.
But Ludvigsson cautioned that the link between ASDs and a positive celiac blood test is based on a small number of cases. There could be a real relationship between the two or it could be a result of doctors overtesting people with ASDs, he said.
"I want to underline that the positive association we found in this small group could be by chance," Ludvigsson said.
The study also does not shed any light on whether a gluten-free diet improves ASD symptoms, he added.
"I think the next step would be for someone to carry out a well-performed study on a gluten-free diet in autism," Ludvigsson said. "There are several such studies, but my understanding is that they haven't been large enough in size."
Green, who was not involved in the new report, agreed that people can't draw any conclusions on gluten-free diets for autism.
"This (study) provides some evidence that there may be a role, but it may also help to find those who would possibly benefit from this therapy," he said.
Ludvigsson, who published his findings in JAMA Psychiatry, said it's also important to examine possible relationships between celiac disease and other "neurocognitive" disorders.
"Our study is definitive when it comes to refuting an association between celiac disease and autism, however, we can't rule out that autism is related to other intestinal conditions that do not fulfill the traditional criteria of celiac disease," he added.