EDNOS

Individuals with clinically significant eating disorders who do not meet the full diagnostic criteria for either anorexia nervosa or bulimia nervosa are currently diagnosed with Eating Disorder Not Otherwise Specified (EDNOS). Individuals with EDNOS may exhibit partial syndromes of anorexia nervosa or bulimia nervosa, show mixed features of both disorders, or have extremely atypical eating behaviors that are not captured by either disorder.

Examples of individuals who should be diagnosed with EDNOS are those who: (1) meet all criteria for anorexia nervosa except have regular menstrual cycles, (2) meet all criteria for anorexia nervosa except their weight falls within normal range, (3) meet all criteria for bulimia nervosa except they engage in binge [Page 224]eating or purging behaviors less than twice per week or for fewer than three months, (4) purge after eating small amounts of food while retaining a normal body weight (i.e., “purging disorder”), (5) repeatedly chew and spit out large amounts of food without swallowing, or (6) meet criteria for binge eating disorder. The body weight of individuals with EDNOS may vary, but those with the binge-eating-disorder subtype (who regularly eat large amounts of food while feeling out of control) are typically overweight or obese.

The EDNOS diagnosis was initially introduced in the 1987 edition of the Diagnostic and Statistical Manual of Mental Disorders as a catchall category for unusual eating disorder presentations. However, data from multiple clinical and nonclinical samples indicate that EDNOS is more prevalent than anorexia nervosa and bulimia nervosa combined. In a community-based sample of approximately 2,000 young females, EDNOS was the most common eating disorder, comprising 2.37 percent of the sample. EDNOS is especially prevalent in populations that have received less research attention such as young children, males, and older adults.

Eating Pathology

Although some forms of EDNOS may represent relatively mild subclinical, prodromal, or residual variants of anorexia nervosa or bulimia nervosa, most individuals with EDNOS exhibit levels of eating pathology and functional impairment commensurate to those with anorexia nervosa and bulimia nervosa. In addition, there is substantial diagnostic crossover between EDNOS and the main eating disorders over time, and rates of EDNOS are elevated in the family members of people with anorexia nervosa and bulimia nervosa.

The high prevalence of EDNOS poses a significant challenge to clinical practice, because to date, no evidence-based treatment has been developed specifically for this disorder. In addition, behavioral geneticists may have difficulty identifying specific genes associated with EDNOS due to the heterogeneity of the disease. In order to ameliorate these concerns, investigators have proposed revising the diagnostic criteria for eating disorders by relaxing the criteria for anorexia nervosa and bulimia nervosa, extracting new diagnoses from the EDNOS category (e.g., binge eating disorder), or collapsing all three disorders (anorexia nervosa, bulimia nervosa, and EDNOS) into a single transdiagnostic category.