Our understanding of the pathophysiological basis of eating disorders (EDs) may be undergoing a revolution. This change may be similar to the transition that has occurred in other psychiatric disorders. For example, 20 years ago, schizophrenia was considered to be caused by psychosocial factors such as `schizophrenogenic' mothers. Today it is well accepted that schizophrenia is caused by an often heritable disturbance of function of brain pathways. A better understanding of the biology contributing to the EDs is important for devising new treatment for these disorders. New treatments are particularly needed for anorexia nervosa (AN) because this illness often has a chronic, relapsing course with a high death rate.
The aetiology of AN and bulimia nervosa (BN) is complex and inยฏuenced by developmental, social, and biological processes. However, the exact nature of these interactive processes remains incompletely understood. Still, there is limited evidence that cultural factors are the primary or most formidable determinants of these disorders. For example, dieting behaviour and the drive toward thinness is quite commonplace in industrialized countries throughout the world, yet AN and BN affect only a small proportion of women.
Emerging evidence suggests that AN and BN are familial disorders with biological correlates. For example, family and twin studies have suggested signiยฎcant genetic inยฏuences in the aetiology of both disorders. Family studies have indicated that the prevalence of eating disorders is seven to 12 times higher in relatives of AN and BN probands compared to controls. Signiยฎcantly higher concordance rates among monozygotic (MZ) relative to dizygotic (DZ) AN and BN twins have suggested substantial genetic inยฏuence in the observed familiality. Indeed, heritability estimates have indicated that approximately 55% to 80% of the variance in AN and BN is accounted for by genetic factors.
It appears that AN and BN are cross-transmitted in families, suggesting they share some common vulnerability. It is possible that anxious, obsessive,