Anorexia redefined as both metabolic and psychiatric

A large-scale genome-wide association study, led by researchers at King’s College London and the University of North Carolina at Chapel Hill (UNC), suggests that anorexia nervosa is at least partly a metabolic disorder, and not purely psychiatric as previously thought. The groundbreaking results of the study have been published in the journal Nature Genetics.

Anorexia nervosa is a serious and potentially life-threatening illness characterised by dangerously low body weight, an intense fear of gaining weight and a lack of recognition of the seriousness of the low body weight. It affects between 1–2% of women and 0.2–0.4% of men and has the highest mortality rate of any psychiatric illness.

Until now there has been uncertainty about the framing of anorexia nervosa because of the mixture of physical and psychiatric features, though researchers have primarily focused on the latter. That all changed when representatives from more than 100 institutions combined data collected by the Anorexia Nervosa Genetics Initiative (ANGI) and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED), with a resulting data set including 16,992 anorexia nervosa cases and 55,525 controls of European ancestry from 17 countries across North America, Europe and Australasia.

The key findings of the study are as follows:

• Eight genetic variants were found to be significantly associated with anorexia nervosa.
• The genetic basis of anorexia nervosa overlaps with metabolic (including glycemic), lipid (fats) and anthropometric (body measurement) traits, independent of genetic effects that influence body mass index (BMI).
• The genetic basis of anorexia nervosa overlaps with other psychiatric disorders, such as obsessive-compulsive disorder, depression, anxiety and schizophrenia.
• Genetic factors associated with anorexia nervosa also influence physical activity, which could explain the tendency for people with anorexia nervosa to be highly active.
   

The study concludes that anorexia nervosa may need to be thought of as a hybrid ‘metabo-psychiatric disorder’, and that it will be important to consider both metabolic and psychological risks factors when exploring new avenues for treating this potentially lethal illness.

“Metabolic abnormalities seen in patients with anorexia nervosa are most often attributed to starvation, but this study shows they may also contribute to the development of the disorder,” said Dr Gerome Breen of King’s College London, who co-led the study. “Furthermore, our analyses indicate that the metabolic factors may play nearly or just as strong a role as purely psychiatric effects.”

“Our findings strongly encourage us to shine the torch on the role of metabolism to help understand why individuals with anorexia frequently drop back to dangerously low weights, even after therapeutic renourishment,” added UNC Professor Cynthia M Bulik, principal investigator on the study. “A failure to consider the role of metabolism may have contributed to the poor track record among health professionals in treating this illness.”

Andrew Radford, Chief Executive of eating disorder charity Beat, concluded, “This is groundbreaking research that significantly increases our understanding of the genetic origins of this serious illness. We strongly encourage researchers to examine the results of this study and consider how it can contribute to the development of new treatments so we can end the pain and suffering of eating disorders.”

Image credit: ©stock.adobe.com/au/alexkich

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