For the first time, scientists have located a genetic variant for anorexia nervosa – an eating disorder that until now was believed to be entirely psychiatric in nature. Genetic variation refers to the variation in the DNA sequence in the human genome. 
Researchers at King’s College London, the University of North Carolina, and Stanford University found that people with anorexia had a genetic variant on chromosome 12, but those without the disorder did not. This chromosome has been associated with type 1 diabetes and autoimmune disorders.
The finding could lead to new or repurposed treatments for anorexia. Currently, anorexia is treated with cognitive analytic therapy (CAT), cognitive behavior therapy (CBT), interpersonal therapy (IPT), focal psychodynamic therapy, and family therapy.  
It also sadly means that anorexia patients could pass the disease to their children. 
Prior to the study, anorexia nervosa was thought to be fueled by a combination of physical, social, and environmental triggers, including anxiety, depression, and the West’s obsession with thinness and outward appearance. 
Teasing Out the Genetic Connection
For the research, the scientists compared the genetic code of 3,495 individuals with anorexia to that of 10,982 healthy people. 
The team found faulty genes in over half of the anorexic patients they analyzed – genes that are associated with neuroticism, schizophrenia, and metabolism.
Professor Cynthia Bulik, of the University of North Carolina, said:
“Anorexia nervosa was significantly genetically correlated with neuroticism and schizophrenia, supporting the idea that anorexia is indeed a psychiatric illness.” 
However, Bulik added:
“We identified one genome-wide significant locus for anorexia nervosa on chromosome 12, in a region previously shown to be associated with type I diabetes and autoimmune disorders.
We also calculated genetic correlations — the extent to which various traits and disorders are caused by the same genes. Anorexia nervosa was significantly genetically correlated with neuroticism and schizophrenia, supporting the idea that anorexia is indeed a psychiatric illness.
But, unexpectedly, we also found strong genetic correlations with various metabolic features including body composition (BMI) and insulin-glucose metabolism. This finding encourages us to look more deeply at how metabolic factors increase the risk for anorexia nervosa.” 
The researchers are continuing to increase their sample sizes and view the outcome of the study as the beginning of genomic discovery in anorexia nervosa.
 Psych Central
 The Telegraph