Characteristics and stability of empirically derived anorexia nervosa subtypes: towards the identification of homogeneous low-weight eating disorder phenotypes.

With the recent publication of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013), issues of nosology are at the forefront of the psychopathology literature. Interest in the development of a more valid diagnostic system has been particularly pronounced for the eating disorders (EDs) (for review, see Keel, Brown, Holland, & Bodell, 2012). Although there is evidence that the DSM-5 ED categories represent an improvement over previous nosological schemes, particularly in decreasing the frequency of ED not otherwise specified diagnoses (Birgegard, Norring, & Clinton, 2012; Keel, Brown, Holm-Denoma, & Bodell, 2011; Machado, Goncalves, & Hoek, 2013), a number of potential limitations remain (Birgegard et al., 2012; Fairburn & Cooper, 2011). DSM-5 is intended to be a “living document with a permanent revision infrastructure” (Regier, Narrow, Kuhl, & Kupfer, 2009, p. 649); thus ongoing efforts to inform ED classification are critical. Moreover, in light of the growing interest in alternative approaches to classifying mental disorders on the basis of underlying mechanisms– as exemplified by the Research Domain Criteria (RDoC) initiative from the National Institute of Mental Health (Sanislow et al., 2010), the elucidation of ED phenotypes that may be linked to distinct etiologic processes could have important implications for research and clinical practice. There are few mental disorders for which novel conceptualizations are needed more than anorexia nervosa (AN). AN is a serious ED associated with substantial morbidity and mortality (Arcelus, Mitchell, Wales, & Nielsen, 2011; Attia, 2010). Yet, little is known about mechanisms that underlie the expression and maintenance of AN symptoms (Attia, 2010), and evidence-based treatments are scarce, especially for older adolescent and adults, who comprise the majority of AN patients (Bulik, Berkman, Brownley, Sedway, & Lohr, 2007). One challenge in designing studies of AN relates to the substantial within-group heterogeneity in symptom presentation that characterizes the illness. Although individuals with AN, by definition, share the symptom of extremely low body weight, they may differ with respect to other ED features such as binge eating, compensatory behaviors, and fear of fatness. This symptomatic heterogeneity poses problems for research on etiology and treatment. For example, biological components like those included in the RDoC matrices are far more likely to be linked to specific behaviors or symptoms than to diagnostic categories (Der-Avakian & Markou, 2012). Likewise, efforts to develop novel treatments may show limited promise if a “one-size-fits-all” approach is applied to a group of individuals characterized by variable symptoms and underlying mechanisms. Thus, the overall goal of the current study was to identify homogeneous subtypes of AN, and examine their short-term stability using empirical methods. A secondary aim was to document predictors of class membership and transition to generate hypotheses about characteristics that might be linked to particular AN phenotypes.