Anorexia Nervosa Epidemiology

Epidemiology
The prevalence of anorexia nervosa among women in the United States and western Europe is between 0.7% and 2.1% of the population. Males constitute 10-15% of patients with anorexia nervosa.

Etiology & Pathogenesis
A. Biological Factors: The number of hormonal changes in anorexia nervosa, as outlined above, suggests a hypothalamic-endocrine origin. However, the changes all appear to be secondary to the effects of starvation, weight loss, malnutrition, and stress, and no evidence of primary hypothalamic dysfunction has been adduced in any of the cases.

There is an increased risk for the disorder in biological siblings of patients with anorexia nervosa, and recent studies have shown a higher concordance rate for monozygotic than for dizygotic twins. However, the fact that anorexia nervosa tends to occur primarily in individuals of the upper and middle socio-economic classes, and the trend for rates to increase in societies in accordance with exposure to Western culture, argue against an exclusive biological origin. Given that the physiological changes in anorexia nervosa (primary or secondary) definitely contribute to its pathogenesis, the clinical features must be viewed as resulting from interacting biological and psychological factors.

Despite its high association with affective disorders, anorexia nervosa is not viewed as simply a variant of affective illness. This is so because the unrelenting pursuit of thinness and distortion of body image are not typical of affective disorders and because the natural course and outcome of anorexia nervosa differ from those of affective disorders.

B. Psychological Factors: A number of psychological theories have been proposed to account for anorexia nervosa. Classical psychoanalysts have emphasized the avoidance of sexuality. They view self-starvation as a rejection of the wish to be pregnant and refusal of food as a behavioral response to fantasies of oral impregnation. Amenorrhea has been viewed as a symbolic manifestation of the wish to be pregnant. More recently, theorists have stressed impairment in the mother-child relationship as the primary cause. Such theorists view the characteristic struggle for autonomy as a manifestation of the failure to master conflicts associated with the process of separation and individuation. The cognitive and perceptual deficits associated with anorexia nervosa, such as the distortion of body image, may also arise from impairments in early childhood development. For example, repeated invalidation of a child's perceptions by overly intrusive parents who "know too well" what a child thinks, feels, and needs can result in development of a sense of personal mistrust characteristic of patients with this disorder.

In recent years, family systems theorists have argued that anorexia nervosa is the result of dysfunctional family interactions. The function of the child who develops anorexia nervosa is to maintain the status quo, allowing the family to remain enmeshed, overinvolved, rigid, overprotective, and unable to handle conflicts openly. The child's illness may also provide the vehicle through which parents are able to fulfill their own unresolved dependency needs.