Eating disorder not otherwise specified presentation in the US population.

Eating disorders represent a significant public health concern because they are associated with serious medical and psychiatric morbidity, role impairment, and often go under-treated.1,2 The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR)3 currently includes three eating disorders: (i) anorexia nervosa (AN), restricting and binge/purge subtypes; (ii) bulimia nervosa (BN), purge and non-purge subtypes; and (iii) eating disorder not otherwise specified (EDNOS). The DSM is first and foremost a clinical tool and designed to guide clinical practice. However, the prevalence and heterogeneity of EDNOS in clinical settings are problematic and may limit the usefulness of the DSM-IV eating disorder criteria. Preparation for the fifth edition of the DSM has led to the re-evaluation of the significance of the current classification system with specific consideration being afforded to the category of EDNOS.4 The “not otherwise specified” (NOS) category in DSM-IV typically refers to a group of individuals that falls outside the main diagnostic categories. Consequently, EDNOS has received less empirical attention,5 which has lead to limited knowledge about the prevalence and clinical characteristics of EDNOS. Several recent studies of clinical samples of adolescents6 and adults,7–13 as well as a meta-analyses of the relationship between EDNOS and the official eating disorder diagnoses,14 indicate that the majority (well over 50% across studies) of adolescents and adults presenting for eating disorder treatment are diagnosed with EDNOS. On the other hand, a recent study of college students showed that proposed DSM-5 diagnostic criteria significantly reduce reliability on EDNOS.15 Nonetheless, the heterogeneity of an EDNOS diagnosis is problematic and limits the information conveyed with this classification. Relatively precise sets of diagnostic criteria are mapped out for AN and BN, and DSM-IV defines the preliminary research criteria for one type of EDNOS (binge eating disorder [BED]), yet no other criteria for EDNOS are specified.16 Thus, EDNOS is a combination of individuals who narrowly fall short of meeting full criteria for AN and BN, those with BED, as well as a variety of other poorly defined presentations. Taken together, and as we have argued before,6 the diagnosis of EDNOS is unwieldy for at least three reasons: first, the majority of patients presenting for eating disorder treatment are assigned a diagnosis that was intended to be a residual category, second, little specific information about eating disorder pathology is conveyed in this diagnosis, and third, this diagnosis fails to convey much information about appropriate treatment strategies. Systematic research that improves the description of EDNOS or investigates efficacious treatments for individuals with EDNOS remains sparse. Several have been proposed, however, there is limited agreement regarding potential resolutions to this diagnostic conundrum. For instance, some have argued for the relaxation of the strict diagnostic criteria for AN or BN, which would allow for the reclassification of individuals with EDNOS based upon specific clinical features such as weight loss or binge eating and/or purging.12,16–18 The remainder of EDNOS could then be subdivided into specific types or potentially distinct disorders (e.g., individuals who purge without binge eating).19 Another, and perhaps more radical proposal, is to highlight the similarities rather than differences between individuals with eating disorders, also referred to as a ‘transdiagnostic’ solution to the problems of nosology16 based on the lack of differences between subthreshold AN and BN and their full-syndrome counterparts.12 However, the latter approach may overlook meaningful differences between EDNOS subgroups.19 A recent study of EDNOS in adolescents further complicates this depiction by highlighting similarities between AN and BN on the one hand that in turn differ from the EDNOS subgroups on the other.6 The present study was designed to add to the growing body of literature on EDNOS in order to provide information that may inform the validity of the classification system of eating disorders. Prior studies have focused on clinical samples with little information available about the presentation of EDNOS in the population at-large. Therefore, the first goal of our study was to describe the relative distribution of AN, BN, and EDNOS in two large population-based surveys, the National Comorbidity Survey Replication Adolescent Supplement (NCS-A) sample of adolescents, and the National Comorbidity Survey Replication (NCS-R) sample of adults. NCS-A was a population-based sample of adolescents aged 13–18 years and NCS-R was a separate survey for adults over 18 years of age. The prevalence rates of eating disorders and subtypes thereof in adults1 and adolescents2 were presented in earlier publications. Our second goal was to examine comparisons between AN, BN and EDNOS on a variety of clinically meaningful indicators and to describe the range of EDNOS presentations on these indicators. These comparisons allowed us to specifically examine the prevalence, clinical severity, and heterogeneity of EDNOS in these large population-based surveys of adolescents and adults. Third, data from this examination may suggest revisions to the DSM, which could have significant implications for clinical research and practice, as well as for public policy.