Genetics may explain susceptibility to anorexia
Researchers have found a gene variant that is more common among people with anorexia. The finding suggests that anorexia is not simply a mental disorder.
Studies of twins have shown that some individuals can have a genetic predisposition to anorexia.
But researchers now have found a genetic difference between anorexia patients and a control group of individuals without anorexia. The study comprises 14,000 participants from several countries, including Norwegians.
The gene variant researchers found in some individuals with anorexia is thought to interfere with metabolism.
"The genetic variation occurs more frequently in those who have anorexia than in the control group, and may probably mean that it makes people more vulnerable to developing anorexia," explains Ted Reichborn-Kjennerud, a professor of psychiatry at the Norwegian Institute of Public Health.
He was part of the research group that recruited Norwegian participants for the study. The findings were recently published in The American Journal of Psychiatry.
More than a mental disorder
Reichborn-Kjennerud, who heads the Department of Mental Health at the Norwegian Institute of Public Health, says the find is quite interesting.
"This suggests that our view of anorexia as solely a mental disorder may be too narrow," he says.
This could help lessen the stigma that is associated with anorexia, he says.
“It’s possible this could help. There are plenty of anorexics who are told that they just have to get their act together and start eating,” Reichborn-Kjennerud says.
Same genetic type as type 1 diabetes
A gene variant is a special type of one or more genes in a particular area on a chromosome.
“This does not mean that everyone who has this gene variant will develop anorexia. Diseases like anorexia are complicated and involve the interaction between many genes and environmental factors,” Reichborn-Kjennerud said.
However, genetic factors can make a person more vulnerable to a disease.
The same genetic variant is associated with type 1 diabetes and autoimmune diseases such as arthritis.
"Maybe we will someday look at anorexia not only as a mental disorder, but also as a metabolic disease," he said.
But how does this gene variant actually affect the development of anorexia?
"We think that something happens to the turnover and metabolism of nutrients in the body, since we know that this same gene variant is also involved in type 1 diabetes and in the regulation of glucose and fat metabolism,” Reichborn-Kjennerud said.
"Something may happen to the ability of this group to regulate their metabolism, if, for example, they begin to lose weight," he explains.
May be more genes involved
Reichborn-Kjennerud points out that it will take more studies to further clarify why some people develop anorexia.
He believes that researchers will eventually find many more genetic variants that help explain the development of the disease in some people but not in others.
"For example, if researchers could increase the number of participants with anorexia to 30,000, compared to 3,000 who were involved this last study, they will likely find that there are more genes involved. This is what happened with schizophrenia, where researchers eventually found more than 150 gene variants that constitute vulnerability factors,” he said.
May lead to new drugs for treatment
Reichborn-Kjennerud hopes the find will help researchers better understand the physical mechanisms that may contribute to the development of anorexia.
"If anorexia is recognized as both a mental and a metabolic disease, it may encourage drug companies to try to develop medications for treatment," he says.
The treatment of anorexia can be quite difficult.
The study was conducted by an international research group of roughly 220 researchers from around the world.
Gun Peggy Knudsen, an area director from the Norwegian Institute of Public Health, also participated in the effort.
"Without broad international cooperation, it would not have been possible to assemble such a wide range of patients with anorexia and healthy people in a control group — which is what enabled us to discover that the disease has both metabolic and psychiatric roots," Knudsen said.
- Abstract: L. Duncan et al: Significant Locus and Metabolic Genetic Correlations Revealed in Genome-Wide Association Study of Anorexia Nervosa. American Journal of Psychiatry. https://doi.org/10.1176/appi.ajp.2017.16121402