Eating disorder not otherwise specified

Eating disorder not otherwise specified (EDNOS) is an eating disorder that does not meet the criteria for anorexia nervosa or bulimia nervosa. Thus, individuals who have clinically significant eating disorders that do not meet DSM-V criteria for anorexia nervosa or bulimia nervosa are diagnosed with EDNOS. Individuals with EDNOS usually fall into one of three groups: subthreshold symptoms of anorexia nervosa or bulimia nervosa, mixed features of both disorders, or extremely atypical eating behaviors that are not characterized by either of the other established disorders. In other words, EDNOS acts as a default category, and is defined by what it is not. Currently, EDNOS is the most commonly diagnosed eating disorder in clinical settings. Because little is known about the symptoms, course, and outcome of this heterogeneous category, the preponderance of EDNOS in clinical practice impedes clinical communication, treatment planning, epidemiological inquiry, primary prevention, and basic research.

As EDNOS was initially thought to be rare, and as 5 of the 6 proposed DSM-5 EDNOS presentations are well-defined, it seems likely that the "residual" (undefined) presentation accounts for most of the 40% of eating disorder cases diagnosed as EDNOS. Research is required into how many of these "residual" EDNOS diagnoses were eventually replaced by that of a recognised medical condition, whether psychologically or organically caused. While all organic causes should be ruled out prior to making a diagnosis of an eating disorder, in practice this is difficult as many physical conditions can also result in low weight, and may develop over time.

Characteristics
Rather than providing specific diagnostic criteria for EDNOS, DSM-IV lists six non-exhaustive example presentations, including individuals 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 the normal range
 * 3) Meet all criteria for bulimia nervosa except they engage in binge 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
 * 5) Repeatedly chew and spit out large amounts of food without swallowing
 * 6) Meet criteria for binge eating disorder

Epidemiology
Although EDNOS (formerly called “atypical eating disorder”) was originally introduced in DSM-III to capture unusual cases, it is now the most commonly diagnosed eating disorder. Specifically, EDNOS accounts for approximately 40% to 60%   of cases in eating disorder specialty clinics, and up to 90% of eating disorder diagnoses conferred in non-specialty psychiatric settings. The lifetime prevalence of EDNOS in the National Comorbidity Survey Replication, a large epidemiological study that interviewed a nationally representative sample of U.S. residents, was 4.64% among adults and 4.78% among adolescents. EDNOS is an especially prevalent category in populations that have received inadequate research attention such as young children, males, ethnic minorities, non-Western groups, and the elderly, which is likely due to anorexia and bulimia nervosa's criteria being based upon observations of white adolescent females.

Presentation and course
Despite its subclinical status in DSM-IV, available data suggest that EDNOS is no less severe than the officially recognized DSM-IV eating disorders. In a comprehensive meta-analysis of 125 studies, individuals with EDNOS exhibited similar levels of eating pathology and general psychopathology to those with anorexia nervosa and binge eating disorder, and similar levels of physical health problems as those with anorexia nervosa. Although individuals with bulimia nervosa scored significantly higher than those with EDNOS on measures of eating pathology and general psychopathology, EDNOS exhibited more physical health problems than bulimia nervosa.

Importantly, an EDNOS diagnosis may presage future diagnostic crossover into officially recognized eating disorder categories. For example, 40% of individuals with EDNOS go on to develop anorexia nervosa or bulimia nervosa within one to two years.

Medical complications
The many health problems associated with EDNOS are varied due to the heterogeneous nature of the diagnosis, are both psychological and physical, and vary greatly in severity. They include:
 * Osteoporosis
 * Ketoacidosis
 * Cardiac dysrhythmias
 * Pseudo Bartter syndrome
 * Oral problems - cheilosis, gingivitis, sialadenosis, etc.
 * Hypoglycemia
 * Iron Deficiency Anemia

Problems with the EDNOS diagnosis
The preponderance of EDNOS in clinical practice poses many clinical and research challenges. Since EDNOS comprises so many heterogeneous presentations, no evidence-based treatment has been developed specifically for EDNOS, and geneticists have not been able to identify specific genes that confer EDNOS risk. Even though EDNOS is a serious eating disorder, health insurance companies may not provide coverage commensurate to that of anorexia or bulimia nervosa, and patients may find the diagnosis invalidating.

Proposed Changes to DSM-5
To address these concerns, the DSM-5 Eating Disorders Work Group has proposed several revisions to the diagnostic criteria, which they hope will reduce the reliance on EDNOS in clinical settings, and promote treatment-seeking and research among affected individuals. Specifically, DSM-5, which is scheduled for publication in spring 2013, will likely expand the diagnostic criteria for anorexia nervosa and bulimia nervosa, and elevate binge eating disorder to a formally recognized diagnosis. Furthermore, DSM-5 plans to rename the EDNOS category Feeding or Eating Disorder Not Elsewhere Classified (FEDNEC), and to provide named descriptions of example presentations, including the following:
 * 1) Atypical Anorexia Nervosa in which all criteria for anorexia nervosa are met except that the individual’s weight is within or above the normal range
 * 2) Subthreshold Bulimia Nervosa (low frequency or limited duration) in which all criteria for bulimia nervosa are met except the binge eating and compensatory behaviors occur on average less than once a week and for less than 3 months
 * 3) Subthreshold Binge Eating Disorder (low frequency or limited duration) in which all criteria for binge eating disorder are met, except the binge eating occurs on average less than once a week and for less than 3 months
 * 4) Purging Disorder (PD) in which patients purge without binging; they consume a normal amount of food and typically maintain normal weight
 * 5) Night Eating Syndrome (NES) in which patients have nocturnal eating episodes, or eat a large proportion of their daily calorie intake after dinner
 * 6) Other Feeding or Eating Condition Not Elsewhere Classified which is a residual category for all other cases that are clinically significant but do not meet the criteria for formal eating disorder diagnoses