Adding Dimension to Eating Disorders Classifications

A number of national associations and task forces have proposed developing newer and better ways of classifying mental disorders by adding observed behaviors and neurobiological measures. Drs. Jennifer E. Wildes and Marsha D. Marcus, from Western Psychiatric Institute and the University of Pittsburgh School of Medicine, recently presented three dimensional models for improving eating disorders classifications (Int J Eat Disord.2013; 46:396).

Model 1: Dimensions of eating disorder psychopathology

The first model focuses on psychopathological dimensions that often coexist with eating disorders and that may be involved in the expression of and persistence of eating disorder symptoms. Clinical observers often note that patients with eating disorders will have changes in one symptom without changes in others, which makes remission and recovery hard to define.  Symptom change and diagnostic crossover are common, suggesting that an approach that incorporates symptom dimensions may be more valid than the current method of using categories for diagnosis. However, the number and specific nature of the dimensions that best describe eating disorder psychopathology are still elusive.

Model 2.  Comorbid psychopathologies

The second model incorporates comorbidities in the classification system, based on observations that rates of comorbid psychopathology are high in patients with eating disorders.  A good example of this is the dual-pathway model of bulimia nervosa in relation to dietary restraint and negative affect, as measured by self-report questionnaires such as the Three-Factor Eating Questionnaire (restraint) and the Beck Depression Inventory (negative affect). The authors point out that several issues must be considered before this model can be appliedsuch as the fact that it would not apply to those eating disorders that do not include loss of control or binge eating.

The authors think that including comorbid psychopathology dimensions to eating disorder classifications reflecting the under-controlled, over-controlled, and low psychopathology classes is promising. One drawback, however, is that few studies have used identical measures to characterize these three classes and it is unclear which parts of comorbid psychopathology are most important for differentiating these groups.

Model 3. Neurobiological dimensions

According to the authors, a major criticism of descriptive approaches to psychiatric nosology involves the lack of agreement between current diagnostic categories and findings from clinical neuroscience studies.  Several models of eating disorder psychopathology suggest neurobiological dimensions that may be relevant for classification of eating disorders. The authors use as an example Dr. Michael Strober’s fear conditioning model of anorexia nervosa, which postulates that dysfunctions in neural systems responsible for regulating emotions, especially processes involved in fear-based learning, probably contribute to the expression of disordered symptoms in some persons. Another area of interest involves brain serontonin function, which may help explain binge eating versus extreme dietary restraint and comorbid psychopathology, such as impulsivity versus anxiety and obsessions.

One model the authors think holds promise for improving classification of eating disorders focuses on incorporating neurocognitive dimensions of impulsivity and compulsivity into the classification of psychiatric disorders.  They note that the descriptions of many eating disorders symptoms appear to include impulsive or compulsive components. And, studies using diagnostic interviews and self-report questionnaires consistently have documented the association of impulsive and compulsive disorders and traits to eating disorders. In addition, alterations in several neural circuits related to impulsivity and compulsivity have been identified in persons with eating disorders. Finally, neuropsychological research supports the idea that neurocognitive dimensions related to impulsivity and compulsivity are salient to eating disorders.

The authors concluded that an approach to classifying eating disorders that incorporates multiple dimensional measures may be very useful for advancing treatment of eating disorders.