Anorexia may be a physical illness, as well as psychological

The eating disorder anorexia nervosa has previously been seen as a psychological condition. However, a new study published in the journal Nature Genetics has identified the first eight genes associated with the condition, suggesting that it is related to the body as well as the mind.

Anorexia is an eating disorder which causes a person to deliberately lose weight and often obsess over food or exercise. The weight loss can have severe health impacts and become life-threatening. It has the highest mortality rate of any psychiatric illness. It can affect people of any age or gender but is ten times more common in women, affecting around nine in 1,000.

The researchers, led by King's College London and the University of North Carolina, looked at the DNA of nearly 17,000 people with anorexia in 17 countries. This genetic information was compared to the DNA of 55,525 who had not had anorexia. The study found eight genetic variants in those with the eating disorder. This suggests that the condition has biological origins, as well as mental.

Professor Cynthia Bulik, from the University of North Carolina, said: "Our findings strongly encourage us to shine the torch on the role of metabolism to help understand why some individuals with anorexia nervosa drop back to dangerously low weights, even after hospital-based refeeding," she said.

The genetic variants found overlap with those of other disorders such as obsessive-compulsive disorder (OCD), depression, anxiety and schizophrenia. They also play a role in influencing physical activity which may explain why people with anorexia tend to do more exercise. Among the mutations found in the DNA of those with anorexia were changes to the genetic instructions which control metabolism, especially those involving blood sugar levels and fat. These mutations may explain why people with anorexia are able to starve themselves for longer than the rest of the population.

The researchers now believe that anorexia nervosa should be considered a "metabo-psychiatric disorder" and that metabolic risk factors should also be considered in research of the condition.

Dr Gerome Breen, from the National Institute for Health Research (NIHR), Maudsley Biomedical Research Centre and the Institute of Psychiatry, Psychology and Neuroscience, at King's College London, co-leader of the study, commented: "Metabolic abnormalities seen in patients with anorexia nervosa are most often attributed to starvation, but our study shows metabolic differences may also contribute to the development of the disorder. Furthermore, our analyses indicate that the metabolic factors may play nearly or just as strong a role as purely psychiatric effects."

Chief executive of Beat, the eating disorder charity, Andrew Radford, called for further research so that better treatment for the disorder can be developed. "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."

This research was published in Nature Genetics.