Anorexia nervosa, which according to some estimates affects between 1-2% of women and 0.2-0.4% of men worldwide and which can lead to physical deterioration and death, has a more complex origin than previously thought: its causes, in fact, are not only to be linked to psychiatric disorders (people suffering from anorexia develop a completely distorted perception of their bodies), but also to a series of metabolic abnormalities, caused by several genetic variants. This is demonstrated in a broad study conducted by more than 100 researchers worldwide, coordinated by the University of North Carolina (USA) and King’s College, London. The results were published in the scientific journal Nature Genetics..

To reach their conclusions, the authors analyzed data from the “Anorexia Nervosa Genetics Initiative” and the “Eating Disorders Working Group” of the Psychiatric Genomics Consortium – two major international study programs involving thousands of people across North America, Europe, Asia and Australia. In particular, the researchers used a dataset including just under 17,000 sufferers of anorexia nervosa and 55,500 “controls” (the technical term used for people of the same age, gender and other characteristics but that do not suffer from anorexia nervosa), identifying eight genetic variants that, according to the researchers, predispose people to the illness and also cause other associated diseases and disorders.

In brief, the conclusions reached by the researchers are as follows: the genetic basis of anorexia overlaps with DNA variants that modify the metabolism of sugars (insulin resistance) and fats (regulation of lipid levels and cholesterol metabolism), and that also influence specific physical characteristics (or, in technical terms, anthropometric traits), such as height and body type (on the other hand, there does not appear to be any connection with body mass index, which combines weight with height). However, the study made another interesting discovery: anorexics almost always have a genetic variant that influences physical activity, driving those that have it to be highly active. Finally, the genetic basis of anorexia nervosa also overlaps with the variants of DNA that contribute to psychiatric disorders, such as obsessive-compulsive disorder, depression, anxiety and schizophrenia.

“Metabolic abnormalities seen in patients with anorexia nervosa in the past were most often attributed to starvation, hunger (which unfortunately plays a major role in the life of anorexics, seeing their drastic reduction in food  intake – editor’s note)” explains Gerome Breen, lecturer at King’s College and coordinator of the studio, together with other colleagues, “but our study shows that metabolic differences may also be the cause of anorexia nervosa (and therefore not an effect – editor’s note). Furthermore, our analyses indicate that the metabolic factors may play nearly or just as strong a role as purely psychiatric effects.”

Anorexia, add the researchers in Nature Genetics, may need to be increasingly thought of as a sort of hybrid (a metabo-psychiatric disorder) and, in light of the new discoveries, it will become extremely important to take this “overlap” into consideration when studying new therapies. Anorexia nervosa is currently very difficult to manage, medically, and it is one of the psychiatric illnesses with the highest mortality rate.

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