A new study suggests that anorexia is not a purely psychiatric disorder but is linked to differences in metabolism underscored by genetics.
'What our study means is we can no longer treat anorexia, and perhaps other eating disorders, as purely psychiatric or psychological,' said Dr Gerome Breen at King's College London who co-led the study with researchers at the University of North Carolina at Chapel Hill.
The large study included data from 17 countries and used large-scale genome-wide association methods to identify genetic differences between almost 17,000 people affected by anorexia nervosa and over 55,500 without the disorder.
The researchers identified eight genetic variants that are different in people with anorexia. While the genetic differences overlapped with those found in other psychiatric disorders, such as obsessive compulsory disorder, depression, anxiety and schizophrenia, they were also found to overlap with metabolic factors that influence how the body responds and deals with food intake and activity levels.
'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,' said Dr Breen. 'Furthermore, our analyses indicate that the metabolic factors may play nearly or just as strong a role as purely psychiatric effects.'
Anorexia nervosa is a serious psychiatric disorder, that has the highest mortality rate of any psychiatric illness. Approximately one to two percent of women and 0.2 to 0.4 percent of men are affected by anorexia, which can present with dangerously low body weight, an intense fear of gaining weight and distorted body image. While treatments, such as cognitive behavioural therapy, are available, patients often relapse and may be unable to maintain a healthy weight permanently.
The results from this new study might offer an explanation. The genetic variants linking anorexia and to metabolic differences could explain why it is currently so difficult to treat anorexia. They also offer hope that based on the newly gained insights, new treatments and screening methods might be developed, suggest the researchers.
'This work adds something really important,' said Rebecca Park, a consultant psychiatrist who studies eating disorders at the University of Oxford. 'It gives the message to sufferers and their families, and professionals delivering or developing treatments, that anorexia may not be conceptualised as a solely psychiatric condition. Rather, metabolic factors may contribute too.
'Hopefully over time such findings will lead to novel treatment approaches and begin to shift a culture of blame, that sufferers should just be able to snap out of it.'
The research was published in Nature Genetics.