Study questions the validity of anorexia nervosa subtypes

Research results add support to the classification of bulimia nervosa and anorexia nervosa as two separated eating disorders but question the validity of anorexia nervosa subtypes. The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a widely used and respected clinical tool used to assist clinicians in the diagnosis, classification and treatment of psychiatric illnesses and disorders. Currently, the diagnostic system for anorexia nervosa and bulimia nervosa are recognised as two separate disorders. However, recently, high rates of diagnostic crossover between the two has raised questions regarding the validity of its use for eating disorders. The authors stated that “given the reported high rates of diagnostic crossover and the fact that a diagnosis of anorexia nervosa or bulimia nervosa is made on the basis of positive criteria for a minimum of just 3 months, it is possible that symptom presentation — and therefore assigned diagnosis — at any given time is unstable.” In order to examine the validity of DSM-IV-TR, they studied the diagnostic crossover longitudinally between anorexia and bulimia nervosa. They involved 215 treatment-seeking women (mean age 234.7 years) with a diagnosis of anorexia nervosa or bulimia nervosa were into their longitudinal study. Eating disorder symptom data were collected weekly using the Eating Disorder Longitudinal Interval Follow-Up Examination and DSM-IV-TR diagnoses were assigned \ using the maximum psychiatric status rating scores for the current week and the preceding 12 weeks — that is, a 3-month period, in accordance with the DSM-IV-TR duration criteria. The women were followed up for a total of 7 years. They found that over 7 years, diagnostic crossover was experienced by the majority (nearly three-quarters) of women with anorexia nervosa. Approximately half of the women crossed bi-directionally between the restricting and binge eating/purging subtypes of anorexia nervosa. Although one-third of women with anorexia nervosa crossed over to bulimia nervosa, they were likely to cross back into anorexia nervosa. Furthermore, women with bulimia nervosa were unlikely to crossover to anorexia nervosa. “While acknowledging that the presence or absence of regular binge/purge behaviour may be clinically useful, the finding that these behaviours come and go during the course of the illness in women with anorexia nervosa suggests that the subtypes are not distinctive disorders,” they claimed. The authors surmised that the relatively low rate of crossover between anorexia nervosa and bulimia nervosa support the distinctiveness of the two eating disorders, but that the results do raise the possibility that the transition from anorexia nervosa to bulimia nervosa may represent a change in stage of illness rather than a change in disorder. They stressed that women who cross over from anorexia nervosa to bulimia nervosa are still vulnerable to relapsing into anorexia nervosa, and that the practical implications of this finding support the validity of distinguishing between the two eating disorders. They concluded that the longitudinal data support the diagnostic distinction between anorexia nervosa and bulimia nervosa, but raise questions about the current anorexia nervosa subtyping schema. Reference...