Researchers have found new links between eating disorders and immune system diseases that they say could help inform diagnosis and treatment.
“Our findings support compelling lines of evidence from researchers suggesting that immune system disturbance is both comorbid with psychiatric disorders and can increase risk for illness,” authors said in the study “Eating Disorders, Autoimmune, and Autoinflammatory Disease” (Zerwas S, et al. Pediatrics. Nov. 9, 2017, https://doi.org/10.1542/peds.2016-2089).
Previous studies have found ties between autoimmune diseases and some psychiatric disorders. Authors of this study expanded the research to include autoinflammatory diseases and specifically looked at their links to eating disorders.
The team analyzed the records of nearly 1 million children and adolescents born in Denmark between 1989-2006 and followed until 2012. During that time, 25,984 were diagnosed with an autoimmune or autoinflammatory disease. Of those, 0.6% went on to be diagnosed with an eating disorder.
Using Cox models to calculate hazard ratios, the team found children with an autoimmune or autoinflammatory disease had a 50% higher hazard for an eating disorder — 73% higher hazard for bulimia nervosa, 72% higher hazard for an eating disorder not otherwise specified (EDNOS) and 36% higher hazard for anorexia nervosa.
Hazard levels were especially high for children with an autoimmune disease with gastrointestinal involvement — 74% higher hazard for anorexia and 148% higher for EDNOS. Autoinflammatory disease was linked to a 179% higher hazard for EDNOS.
Hazards were especially high for males. For instance, those with an autoinflammatory disease had a 740% higher hazard for EDNOS, according to the study. However, researchers cautioned confidence intervals were wide.
The team also found that of the 3,914 adolescents with an eating disorder, 2.1% had a subsequent autoimmune or inflammatory diagnosis. Adolescents with anorexia had a 64% higher hazard for autoimmune/inflammatory disease, while those with EDNOS had a 121% higher hazard.
Researchers could not say for certain why eating disorders and immune diseases are linked, but offered theories.
“Eating disorders are commonly associated with reward dysfunction, and neural inflammation can lead to changes in reward functioning including heightened reactivity to threat, increased sensitivity to punishment, and decreased connectivity in reward pathways,” they wrote.
The strong links between eating disorders and autoimmune diseases with gastrointestinal involvement may be a matter of misdiagnosis for some adolescents due to symptoms overlapping, but authors noted the associations held up even when there were no gastrointestinal symptoms.
The team also found that adolescents with a family history of an autoimmune or autoinflammatory disease were more likely to be diagnosed with an eating disorder. Parent-child, sibling and cousin relationships all showed associations between the conditions, but it was not clear whether the ties were due to genetics or environment.
Authors of a related commentary called the study a “significant contribution to the growing body of literature supporting an association between immune system dysfunction and eating disorders.”
“Clinicians are encouraged to consider the possibility that patients with eating disorders may have underlying autoimmune or autoinflammatory conditions,” they wrote. “… Conversely, we must also remain vigilant about the development of eating disorders among patients with autoimmune or autoinflammatory disorders.”
