Eating Disorder Not Otherwise Specified (EDNOS) was a diagnostic term formerly used in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). It served as a residual or “catch-all” category for individuals whose eating disorder symptoms caused significant distress and impairment but did not meet the full, strict criteria for Anorexia Nervosa or Bulimia Nervosa. Although outdated, EDNOS historically represented a large group of people with serious pathology who required treatment. The category ensured that clinically significant conditions could still be recognized and addressed by clinicians.
The Role of EDNOS in DSM-IV
The function of the EDNOS category within the DSM-IV was to provide a classification for patients who exhibited a clear eating disorder that fell outside the rigid diagnostic thresholds for Anorexia Nervosa or Bulimia Nervosa. It acted as a necessary safety net, ensuring that people with genuinely harmful behaviors and psychological distress were not denied a diagnosis simply because they lacked one specific criterion. The code used to identify this diagnosis in the DSM-IV was F50.9.
Clinicians would assign the EDNOS diagnosis when a patient presented with a severe eating disturbance, but their symptom profile did not fully align with the narrow definitions of the primary disorders. This residual category acknowledged the reality that eating disorders manifest across a wide spectrum of presentations. In many settings, EDNOS accounted for the majority of all eating disorder diagnoses, sometimes representing 40% to 60% of cases in specialized treatment centers.
Clinical Presentations That Fell Under EDNOS
The EDNOS category covered a diverse range of conditions, many of which were just as medically dangerous as a full-criteria diagnosis.
Atypical Anorexia Nervosa
One common presentation was Atypical Anorexia Nervosa, where an individual displayed all the psychological and behavioral features of Anorexia Nervosa, including an intense fear of weight gain and restrictive eating. However, their current body weight remained within or above the normal range. These patients often had experienced significant, rapid weight loss.
Low Frequency Bulimia Nervosa
Another frequent diagnosis was Bulimia Nervosa of low frequency or limited duration. This applied to individuals who met all criteria for Bulimia Nervosa, such as recurrent episodes of binge eating followed by compensatory behaviors like purging. These behaviors occurred less often than the required twice-weekly frequency or had been present for fewer than three months. The pathology and physical harm remained present, but the frequency threshold excluded them from a full diagnosis.
Purging Disorder
A third distinct presentation was Purging Disorder, characterized by recurrent purging behaviors, such as self-induced vomiting or misuse of laxatives, aimed at influencing shape or weight. This occurred in the absence of objective binge eating episodes. These examples illustrate how the EDNOS designation was used for serious conditions that were simply “subthreshold” according to the DSM-IV’s detailed checklists.
Why the Terminology Changed in DSM-5
The primary issue with the EDNOS designation was its sheer prevalence, as it was often the most common eating disorder diagnosis, sometimes accounting for over 50% of all cases. This overuse of a “not otherwise specified” label made it difficult for researchers to study distinct presentations and hindered the development of targeted treatments. The category was too heterogeneous, containing patients with widely different symptom profiles and medical risks.
The American Psychiatric Association sought to improve diagnostic specificity in the 2013 revision, the DSM-5. The revision aimed to ensure that more individuals with clinically significant eating disorders received a diagnosis that accurately described their symptoms. Changes included broadening the criteria for Anorexia Nervosa and Bulimia Nervosa, such as removing the requirement for amenorrhea (loss of menstruation) and reducing the required frequency of compensatory behaviors.
The EDNOS category was retired and replaced with two new, more specific residual categories. The first, Other Specified Feeding or Eating Disorder (OSFED), is for cases where the clinician can specify why the criteria for a full diagnosis were not met. The second, Unspecified Feeding or Eating Disorder (USFED), is reserved for situations where there is insufficient information to make a more specific diagnosis, such as in emergency room settings. This structural shift aimed to reduce the number of patients in a vague category and promote better clinical communication.
Defining Other Specified Feeding or Eating Disorder
The category Other Specified Feeding or Eating Disorder (OSFED) now captures the majority of cases that were previously classified as EDNOS. Unlike its predecessor, OSFED requires the clinician to document the specific reason why the patient’s presentation does not meet the full diagnostic criteria for another eating disorder. This mandated specificity is a significant step toward improving research and treatment planning for these patients. The current diagnostic code for OSFED is F50.89.
The DSM-5 provides a list of five specific clinical examples that fall under the OSFED designation, formalizing conditions that were historically lumped together:
- Atypical Anorexia Nervosa, where all criteria for Anorexia Nervosa are met despite the person not being underweight.
- Bulimia Nervosa of low frequency and/or limited duration, which misses the frequency or duration threshold for a full diagnosis.
- Binge Eating Disorder of low frequency and/or limited duration, which misses the frequency or duration threshold for a full diagnosis.
- Purging Disorder, which is recurrent purging behavior in the absence of binge eating.
- Night Eating Syndrome, characterized by recurrent episodes of eating after awakening from sleep or excessive food consumption after the evening meal.
The inclusion of OSFED emphasizes that these conditions are serious, clinically significant, and deserve the same level of attention and treatment as any other specified eating disorder.