Moreover, anorexia - along with other eating disorders - is reported to hit the transgender community relatively hard; around 16 percent of transgender college students reportedly have an eating disorder.
Eating disorders are a serious mental health issue caused by a variety of complex factors, from psychosocial to genetic and biological issues.
Anorexia can be a deadly disease. Of all mental health disorders, anorexia is linked with the highest mortality rate. Death can be a consequence of not receiving treatment, but 1 in 5 anorexia-related deaths are a result of suicide.
New research identifies, for the first time, a significant genetic location that underpins anorexia. Researchers from the University of North Carolina (UNC) School of Medicine in Chapel Hill conducted a genome-wide study in an effort to identify the genetic basis for this psychiatric condition.
The new research was carried out by the Psychiatric Genetics Consortium Eating Disorders Working Group - an international group of researchers from institutions all over the globe - and the team was led by Cynthia Bulik, Ph.D., founding director of the UNC Center of Excellence for Eating Disorders and a professor at Karolinska Institutet in Stockholm, Sweden.
The findings were published in the American Journal of Psychiatry.
Conducting a large, genome-wide study of anorexia
The research consisted of a genome-wide association study examining the DNA of 3,495 people with anorexia nervosa and 10,982 people without.
In genetics, the word "association" refers to a situation in which specific genetic variations - or single nucleotide polymorphisms (SNPs) - are found more frequently in people with a certain disease.
Using standard association analysis, Bulik and team calculated the genetic correlations between anorexia nervosa and 159 psychiatric, education, and metabolic phenotypes. "Phenotypes" refer to the set of observable characteristics that are a result of the interaction between our genes and the environment.
Bulik defines genetic correlations as "the extent to which various traits and disorders are caused by the same genes."
Overall, the study looked at 10,641,224 SNPs.
Anorexia has 'both psychiatric and metabolic roots'
The study revealed strong associations between anorexia and psychiatric as well as, surprisingly, metabolic conditions.
Bulik and colleagues uncovered a genetic locus on chromosome 12: rs4622308. This genetic area has previously been associated with type 1 diabetes and autoimmune disorders, report the authors.
"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 [...] and insulin-glucose metabolism. This finding encourages us to look more deeply at how metabolic factors increase the risk for anorexia nervosa."
Additionally, the study found positive genetic associations between anorexia and educational achievement, as well as high-density lipoprotein cholesterol - that is, the "good" kind of cholesterol. They also revealed negative correlations with the phenotypes for body mass index (BMI), insulin, blood sugar, and lipids.
The authors note that the large scale of the study enabled them to come up with "the first genome-wide significant locus" for the disease.
"In the era of team science, we brought over 220 scientists and clinicians together to achieve this large sample size. Without this collaboration we would never have been able to discover that anorexia has both psychiatric and metabolic roots," notes co-author Gerome Breen, Ph.D., of King's College London in the United Kingdom.