For the first time, scientists have linked a specific region of the genome to anorexia nervosa risk. The findings, published today in the American Journal of Psychiatry, suggest that the serious eating disorder is genetically correlated to other psychiatric characteristics, including schizophrenia and the personality trait of neuroticism. But anorexia is not just a psychiatric issue, the study says: Genes associated with metabolism were also linked to the diagnosis.
"We wanted to take a systematic look at the biology of the disease and find new clues about what might be causing anorexia," said Stanford's Laramie Duncan, PhD, lead author of the new research. (Duncan's role in the work begin at Harvard, where she previously worked, and the study involved several institutions in the United States and the United Kingdom.)
Understanding the cause is important because anorexia is life-threatening and difficult to treat. In recent years other Stanford researchers have demonstrated that involving families in treatment for adolescent anorexia nervosa can be successful, but no existing therapy works for everyone. Treatments that tackle the underlying biology could be better.
The new research examined the complete genetic code of 3,495 people with anorexia and 10,982 control individuals without anorexia. It used a method called a genome-wide association study, which looks for patterns in common genetic variants across large groups of people. Prior research in twins had suggested genetic factors contribute to anorexia risk, but specific genes had never been identified.
Genetic variation in one particular region on chromosome 12 was linked to anorexia risk, the study found. The researchers examined several genes in that area. In sum, they explain about 20 percent of anorexia risk. The new findings do not constitute a genetic test for anorexia, nor can genetic information predict who will or won't develop the disease, Duncan cautioned.
Still, the results are illuminating. The researchers found overlap with genetic risk factors for neuroticism and for schizophrenia, for instance. (A previous analyses showed genetic correlations between anorexia and obsessive-compulsive disorder, they note, which makes sense given that doctors have long seen an overlap between anorexia and OCD diagnoses in their patients.)
Interestingly, the study also suggests anorexia and obesity are two ends of the same biological spectrum. It showed negative correlations between anorexia and genetic risk for obesity.
"We could see that, in some ways, anorexia is the opposite of obesity," Duncan said. "Some of the genetic factors that contribute to obesity are the same as those in anorexia, but people with anorexia have alternate versions of that genetic material."
This finding could change how we view anorexia, Duncan added. "People have thought of anorexia as an exclusively psychological or psychiatric problem," she said, noting that obesity used to be viewed the same way. "But really there's something more metabolic to this, involving genes that affect weight in everyone."
Previously: Celiac disease and anorexia nervosa linked, study shows, Stanford researchers expand comparison of males and females with anorexia and Families can help their teens recover from anorexia, new study shows
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