The influence of genetics on eating disorder development may not make for the sexy headlines that other risk factors provide. But genetics are key in the complex picture of how eating disorders arise in some individuals and not in others.
"Research is consistently demonstrating that genetics play a pivotal role in the etiology of eating disorders," says Dr. Joy Jacobs, a clinical psychologist and eating disorder specialist at the University of California at San Diego. "More specifically, a person's unique combination of genes may ultimately make an individual more (or, alternatively, less) susceptible to developing an eating disorder."
Genetic susceptibility to eating disorders may cause a person to feel the influence of risk factors in her (or his) environment more strongly. These factors include media influence, inappropriate body image ideals promoted by pro-anorexia/pro-bulimia websites, the effects of dieting, abuse and trauma, and others.
But the connection between genetics and environment is complex. A person who is only slightly susceptible to developing an eating disorder would need a major trigger for the disorder to develop. Another may be highly susceptible genetically; this person may develop an eating disorder even after a relatively mild trigger. Further, it's important to remember that no level of genetic susceptibility guarantees that an eating disorder will occur.
Quick Hits on Genetics and Eating Disorders
- The lifetime risk for developing an eating disorder is 10 times greater for relatives of those who have eating disorders than for relatives of those who don't.
- The child of a parent with an eating disorder may have an eating disorder that is different from the parent's.
- Family and twin studies suggest that genetic factors account for more than half of the variance in the development of anorexia nervosa.
- Chromosome 14 has been linked to bulimia nervosa. One gene on this chromosome, the estrogen receptor beta gene, appears to be associated with both bulimia and anorexia.
- There appears to be a significant association between the 5HT(2a) receptor gene (a gene in the serotonin system) and anorexia. Other serotonin-related genes are under investigation.
- A specific gene has been linked to the development of anorexia nervosa, purging type.
- A study suggests that body dissatisfaction and drive for thinness "exhibit moderate to high heritability" in women, though not in men. These two traits are tested by the Eating Disorders Inventory, an eating disorder screening questionnaire.
- Linkage studies, done by examining blood relatives who have eating disorders to see if their genetic makeups have unexpected similarities, suggest that chromosome 10 may play a role in anorexia, bulimia, and possibly other eating disorders.
What Does it Mean?
The knowledge that genetics influence eating disorder development is promising news for the future of eating disorder prevention. We may be able to develop ways to recognize susceptibility and take steps to educate the vulnerable and their families, effectively stopping eating disorders before they start. Future research may even lead to the possibility of medical intervention after an eating disorder already exists.
Also, knowing that there is a significant genetic component behind eating disorders can be relieving for parents. Many parents feel immense guilt, assuming (erroneously) that they must be the cause. But a child's genetic makeup is determined long before the family can exert its influence.
Sources:
Bulik CM. Exploring the gene-environment nexus in eating disorders. Journal of Psychiatry & Neuroscience 30 (2005): 335-339.
Jacobs J. Personal correspondence. 19 February 2009.
Keski-Rahkonen A, Bulik CM, and Neale BM. Body dissatisfaction and drive for thinness in young adult twins. International Journal of Eating Disorders 37 (2005): 188-199.
Klump KL and Gobrogge KL. A review and primer of molecular genetic studies of anorexia nervosa. International Journal of Eating Disorders 37 (2005): S43-S48 (special issue: Anorexia Nervosa).
Ribases M, Gratacos M, Badia A, Jimenez L, Solano R, Vallejo J, Fernandez-Aranda F, and Estivill X. Contribution of NTRK2 to the genetic susceptibility to anorexia nervosa, harm avoidance and minimum body mass index. Molecular Psychiatry 10 (2005): 851-860.
