It has only been during the past couple of decades that we, as a culture, have discussed and addressed eating disorders. The two eating disorders discussed most often are anorexia nervosa and bulimia. Anorexia nervosa has been defined as a serious eating disorder primarily affecting young women in their teens and early twenties, that is characterized especially by an intense fear of weight gain leading to faulty eating patterns, malnutrition, and usually excessive weight loss. Bulimia nervosa has been defined as a serious eating disorder that occurs chiefly in females, characterized by overeating, usually followed by self-induced vomiting, or laxative or diuretic abuse, and is often accompanied by guilt and depression.(1)

In addition to anorexia and bulimia, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), includes the diagnosis of eating disorders not otherwise specified (NOS).(2) Individuals with eating disorders in this category manifest symptoms of eating disorders, but do not meet the diagnostic criteria for a specific eating disorder.

Understanding these disorders is difficult due to the many physiologic, biochemical, developmental, psychological, and psychiatric phenomena associated with them. It is difficult to determine whether some biologic changes are causing the eating disorder, or whether the changes are a result of abnormal eating patterns and eventual starvation.

The medical community has not yet concluded the absolute cause for eating disorders, however there are theories which have gained attention. Abnormalities of the hypothalamic-pituitary-adrenal (HPA), hypothalamic-pituitary-gonadal (HPG), and hypothalamic-pituitary-thyroid (HPT) axes have been described as potential causes of anorexia nervosa.(3) Although many abnormalities in the endocrine systems occur in other forms of starvation, the difference is that in anorexia nervosa, the dysfunction may not improve when weight returns to normal. The role of neurotransmitters has also been extensively investigated, particularly serotonin, as it plays an important role in eating. Norepinephrine has a role in the increase or decrease of hunger sensations, and dopamine may play a part in the self-stimulatory behavior of eating binges in bulimia.

The greatest emphasis, however, is placed on psychological and developmental issues in understanding the origin and cause of eating disorders, especially regarding the role of family. Some of the personal issues that may be involved include family separations, losses, and dysfunction. These may trigger abnormal eating behavior.(3, 4) Whether family-related issues are a cause for eating disorders remains controversial. It is interesting, however, to note that the prognosis is better in persons with a relatively healthy family environment.(5)

Other groups at risk for the development of eating disorders are those with a history of physical and sexual abuse. Also at risk are athletes, particularly female gymnasts, figure skaters, distance runners, and swimmers. Male wrestlers and body builders are included in this risk category as well.

Researchers have determined that up to 68 percent of individuals treated for an eating disorder also have a primary mood disorder.(6) The course of anorexia nervosa most commonly consists of a single episode with a subsequent return to normal weight. Some individuals may experience an unremitting course leading to death, or repeated periods of anorexic behavior.(7) A recent study found that 50 percent of patients had a "good" outcome, 30 percent a "medium" outcome, and 20 percent a "poor" outcome.(8) Long-term follow-up studies have demonstrated that between 10-18 percent of ano