Contrary to popular belief, the origins of anorexia nervosa are not only psychiatric. The metabolism would also have a part to play.
anorexia nervosa, which is mainly characterized by a dangerous weight loss (more than 15% of the initial weight) and a panic fear of taking it, is a serious disease which affects between 1 and 2% of women and between 0.2 and 0, 4% of men in the world. With a 5% to 15% mortality rate, it is the deadliest mental illness there is. However, contrary to what was believed so far, it would not only be a psychiatric disorder but also a metabolic one, according to a study published in the journal Nature Genetics.
By analyzing 16,992 cases of anorexia nervosa in 17 rich countries identified by different databases, around a hundred experts from around the world concluded that the genetic bases of anorexia nervosa also had metabolic, lipid and anthropometric aspects. And this is independent of the genetic effects influencing the Body Mass Index (BMI), assures the study.
Moreover, the genetic basis of this disease overlaps with other psychiatric disorders such as obsessive-compulsive disorder, depression, anxiety and schizophrenia. Finally, genetic factors associated with anorexia nervosa also influence physical activity, which could explain why many anorexics are so active.
A hybrid “metabo-psychiatric” disorder
“The metabolic abnormalities observed in patients with anorexia nervosa are more often attributed to starvation, but our study shows that metabolic differences could also contribute to the development of the disease. Furthermore, our analysis indicates that metabolic factors could play a role almost as important as the purely psychiatric effects”, notes Dr Gerome Breen, of King’s College London, who co-led the study.
“Over time, there has been uncertainty about the label of anorexia nervosa due to its physical and psychiatric aspects. Our results confirm this duality and suggest that integrating metabolic information could help healthcare professionals to develop better ways to treat eating disorders,” said Professor Janet Treasure (King’s College) who also took part in the study. In particular, this could help to understand why some individuals relapse into the disease even after being fed for a long period in hospital.
Thus, anorexia nervosa should perhaps be considered a hybrid “metabo-psychiatric” disorder, the researchers note. “This is groundbreaking research that significantly increases our understanding of the genetic origins of this serious disease. We urge researchers to review the results of this study and consider how it might contribute to the development of new treatments so that we may come to end of eating disorders”, concludes Andrew Radford, director of Beatthe UK’s leading eating disorder charity.
The disease most often begins during puberty
In France, according to a study conducted in 2008 among adolescents, anorexia nervosa affected 0.5% of young girls and 0.03% of boys between 12 and 17 years old. Because the disease is most often triggered between 14 and 17 years old, with a peak of maximum prevalence at 16 years old.
According to Insermits diagnosis is based on the following criteria: the way of eating (restriction, avoidance of certain foods), certain practices (induced vomiting, taking laxatives), weight (BMI less than 17.5 kg/m2) and the absence of periods for at least three months for girls. The refusal to recognize one’s thinness, the distorted perception of one’s body and the fear of getting fat are also symptoms of the disease. Finally, the slowing of growth in a young adolescent as well as hyperactivity, food obsessions and intellectual over-investment should also alert parents.
On average, the anorexic phase lasts one and a half to three years, but this state can last up to five years. After this period, two thirds of patients are cured. If the others have “chronic anorexia nervosa”, later remissions are possible. “In the end, half of people treated for anorexia nervosa in adolescence recover, a third is improved, 21% suffer from chronic disorders and 5% die”, notes Inserm recalling that most deaths occur the year following the release of hospital, most often by suicide (27% of cases).
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