But a new study suggests that the two disorders share some symptoms. Moreover, they may be confused for each other initially, and they could be linked in other interesting ways, the study found.
The researchers found that women who have celiac disease have a slightly increased risk of being diagnosed with anorexia nervosa at a later time.
What's more, the connection is also true the other way around: Individuals with anorexia nervosa are somewhat more likely than other people to later be diagnosed with celiac disease, according to the findings, published online today (April 3) in the journal Pediatrics. [5 Ways Gut Bacteria Affect Your Health]
Taken together, these findings suggest that people with celiac disease might have been misdiagnosed with anorexia previously, and that some people with celiac disease may go on to develop anorexia nervosa, said Dr. Neville Golden, chief of adolescent medicine at Lucile Packard Children's Hospital Stanford, who was not involved in the new study.
Golden and his colleague Dr. K.T. Park, a pediatric gastroenterologist also at Stanford, wrote an editorial accompanying the study that was published in the same issue of Pediatrics. In the editorial, they also speculated that the link between celiac disease and anorexia could suggest a shared genetic susceptibility to both conditions.
Finding a link
People with anorexia nervosa have an intense fear of gaining weight, and they may have an abnormally low body weight. People with celiac disease have an immune system response in the small intestine whenever they eat gluten, a protein found in wheat, barley and rye. Over time, this immune reaction can damage the small intestine's lining.
In this new study, the researchers gathered information from a nationwide patient database in Sweden. They reviewed data from the medical records of about 18,000 girls and women of all ages who lived in Sweden in 1987 or later and who had been diagnosed with celiac disease and had undergone a biopsy of their small intestine to confirm this diagnosis between 1969 and 2008. The analysis also looked at a comparison group of about 89,000 Swedish women of similar ages.
The average age of the women at the time they were diagnosed with celiac disease was 28, according to the findings.
The researchers found that the women who were diagnosed with celiac disease before the age of 19, were 4.5 times more likely to have been previously diagnosed with anorexia nervosa, compared with women who didn't have celiac disease. This association held true even after the researchers took into account factors known to be linked with women's risk of developing celiac disease, such as socioeconomic status, education and type 1 diabetes, the findings showed.
The study also showed that women ages 20 and older had almost twice the risk of developing anorexia nervosa after receiving an initial diagnosis of celiac disease, compared with women who didn't have celiac disease.
Previous research has suggested a connection between celiac disease and anorexia, but most of the evidence for this association has come from individual case reports and not from population-based studies such as this one.
This is the first large study to show an association between celiac disease and anorexia nervosa, both before and after celiac disease has been diagnosed, said the study's lead author, Dr. Karl Marild, a pediatrician and a postdoctoral fellow at the Barbara Davis Center for Diabetes at the University of Colorado, in Aurora, Colorado.
Scientists don't really know the exact biological explanation for why celiac disease and anorexia might be linked, Marild told Live Science. [Top 10 Mysterious Diseases]
One explanation may be that people with celiac disease or anorexia may be misdiagnosed with the other condition, which would result in a delay of appropriate treatment, Marild suggested.
Celiac disease and anorexia may be misclassified because the two illnesses have some similarities, such as some common gastrointestinal symptoms that could make it difficult for doctors to distinguish one medical problem from the other. People affected by either condition may complain of stomach pain, bloating, weight loss and fatigue, Marild said. In addition, when these disorders occur in tweens and teens, they may cause stunted growth and a delayed onset of puberty.
Although this research was done in Sweden, there are a few smaller studies from the United States that have also indicated that patients with celiac disease may develop eating disorders, including anorexia, Marild said.
This may occur because these individuals may focus excessively on their diets to eliminate foods with gluten, which may trigger disturbed eating patterns in susceptible individuals, he suggested.
One limitation of the study was that the researchers lacked dietary data, such as the level of adherence to a gluten-free diet among the women with celiac disease, Marild noted.
Originally published on Live Science.