Heritability, genetics and association findings in anorexia nervosa

Anorexia nervosa (AN) is a severe psychiatric disorder, characterized by a combination of abnormal eating behavior and weight regulation with disturbances of attitudes toward body weight and shape. Prevalence is estimated at 1/1000, but with a high prevalence of the partial syndrome and a 10% mortality rate. This article reviews the findings concerning the heritability and the contributing genes of the disorder, with a focus on candidate genes. In family studies, a higher frequency of AN and BN was found among relatives of AN probands. The heritability rate was estimated at 0.71, similar to twin studies, which estimate 0.58-0.76. The search for genes responsible for the disorder focuses on the monoaminergic and peptidergic systems that are related to appetite and weight regulation. So far, for serotonin and dopamine there are no consistent findings in association studies of AN. However, in an Israeli study, an association was found between susceptibility for AN and the COMT gene, which is involved in monoamine metabolism. Another Israeli study found a relation between AN and the gene encoding for the potassium channel (hSKCa3), which is involved in regulation of neuronal activity. In the endocrine system an unequivocal finding was described of an association to the gene encoding the receptor for beta-estrogen. In the appetite and weight regulation system an association was described between AN and a marker of the uncoupling protein-2 and -3 chromosomal region, raising the likelihood that the mutation within the gene is close to a positive marker. To conclude, although there is a strong familial component in AN, so far the search for candidate genes has not been fruitful and further large scale prospective and adoption studies are needed to confirm genetic factors. We hope that relative studies using a wide genome scan, as well as subtyping the different types of AN, will bring us closer to understanding of the heritability of AN and enable the development of improved means of prevention and treatment.