Genetic influences in the development of eating disorders

Introduction Eating disorders (EDs) presenting in childhood are complex conditions. Current aetiological models thus emphasize multifactorial determinants. This chapter focuses on the genetic factors influencing the development of EDs. Further details can be found in this volume on family factors (see Lock & Couturier, Chapter 19), individual factors (see Bryant-Waugh, Chapter 9; Hay & McDermott, Chapter 18) and environmental issues including emotional trauma (see Brewerton, Chapter 13). Evidence of genetic influences Family and twin studies Family studies have shown that anorexia nervosa (AN) is more common among relatives of probands than among relatives of normal controls or among relatives of non-anorexic psychiatric patients (reviewed in Gorwood et al., 2003). Similarly, studies on probands with bulimia nervosa (BN) have shown higher rates of BN among first-degree relatives (Strober et al., 2000). Twin studies have been used to distinguish between the genetic and the environmental contributions to the familial liability observed in EDs. About 38-55% of the identical (monozygotic, MZ) twins described in the literature were concordant for AN (Kipman et al., 1999). This rate is greater than would be expected from prevalence data, and is also much higher than the fraternal (dizygotic, DZ) twins concordance rate (0-11%). Systematic controlled twin studies have also reported a higher concordance rate among MZ twin sisters than among DZ (55-56% vs. 5-7%) (Holland et al., 1984, 1988).