A New Advance in Understanding Anorexia Nervosa
An important genetic study increases our understanding.
Posted Sep 18, 2019
Anorexia nervosa (AN) is a disabling and life-threatening illness characterized by food restriction, significantly low body weight, fear of gaining weight or becoming fat, and a distorted perception of one’s own body weight or shape. This illness, like most psychiatric disorders, is associated with alterations in cognition, motivation, and emotion. About 1 percent of women suffer from this disorder; it is much less common in men.
Advances in genetics and molecular biology have made it possible to identify genes that contribute to the development of specific medical disorders. For most psychiatric disorders, many genes each contribute to the risk of an individual developing a psychiatric disorder; over 100 genes for common disorders studied to date).
In a study recently published in Nature Genetics, researchers compared genetic information from 16,992 individuals with anorexia nervosa with genetic information from 55,525 control individuals. Their analysis provides evidence that AN is both a psychiatric and metabolic disorder. The authors conclude by using the term “metabo-psychiatric” to describe the illness.
Consistent with recent reports demonstrating shared genetics across a variety of psychiatric illnesses, the results of this new study indicate that AN is genetically related to multiple other psychiatric disorders, including obsessive-compulsive disorder, anxiety disorders, depressive disorders, and schizophrenia. In addition, they found that AN likely involves genes that regulate metabolism, hunger, and appetite. There are also genes involved in regulating body size parameters such as waist size and hip size, and AN is genetically related to these as well.
The results of this study indicate that genes regulating body size/shape and metabolism may partially underlie AN, and that genes related to metabolic processes could be a central reason why individuals with AN feel the need to lose weight. Thus, the desire of AN patients to be thin may reflect metabolic dysfunction and not purely abnormal psychology.
Psychological improvement can occur when persons suffering from AN are able to gain back a certain amount of weight. Because genes may be involved in the drive for thinness, it is very difficult for individuals with AN to reach a healthy weight and then maintain a body weight that is associated with physiologic and psychologic improvement. In effect, AN patients are trying to buck genetically-regulated metabolic demands.
The authors hope that the results of their study stimulate new treatment approaches. Perhaps therapies targeting some of the metabolic systems involved in this disorder may prove to be effective additions to the current psychotherapeutic and psychopharmacologic treatments. AN is a complex set of illnesses desperately in need of new and more effective treatments, so these new results offer hope going forward.
This post was written by Eugene Rubin, MD, Ph.D., and Charles Zorumski, MD.
Watson, H.J., et al. (2019). Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa. Nat Genetics. 51: 1207-1214.