The Instability of Eating Disorder Diagnoses

Eating disorders diagnoses may fluctuate far more than one might suspect, according to results of a recent prospective study by Dr. Christopher G. Fairburn and colleagues at Oxford University and University Hospital, Zurich. In this study, two-thirds of patients originally diagnosed with a specific eating disorder had a different eating disorder diagnosis 30 months later (Br J Psychiatry 2005;187:573).

A sample of 192 women with current DSM-IV eating disorders (55 with anorexia nervosa [AN], 108 with bulimia nervosa [BN], and 29 with an eating disorder not otherwise specified [EDNOS]), were interviewed three times over 30 months.

Migration between diagnoses

Although remission from an eating disorder was uncommon, migration between the eating disorder diagnoses occurred in more than half of the study participants. Sixty-two women, or 53%, crossed over from one eating disorder diagnosis to another. This migration was evident in all three groups. Thus, of the 55 women initially diagnosed with AN, only 31 (56%) retained the diagnosis at 12 months and just 27 (49%) still had the diagnosis at 30 months. Twenty-three women with an initial diagnosis of AN (48%) retained this diagnosis at both reassessments.

Change in diagnosis was even more evident among those with BN. Of the 108 participants with BN at baseline, only 55 (51%) had this diagnosis at the first reassessment and just 40 (37%) had it at the second assessment. Those with EDNOS also had changing diagnoses. Of the 29 women with EDNOS at baseline, just 8 (28%) still had the diagnosis at 12 months and 9 (31%) at 30 months. Only 3 (10%) had EDNOS at both reassessments.

Purging behavior

At all three assessment points, participants’ diagnoses were classified as either purging or non-purging, using the DSM-IV threshold frequency of purging behavior (vomiting or use of laxatives) at least twice a week. At baseline, 58 (30.2%) of diagnoses were classified as non-purging and 134 (69.8%) as purging.

After excluding the 25 women who had stable remissions (no eating disorder diagnosis at both follow-up assessments), analyses showed that 65 of `121 participants with a baseline purging eating disorder (53.7%) had been given a non-purging diagnosis. Of 46 participants with a non-urging diagnosis at baseline, 8 (17.4%) subsequently had a purging diagnosis.

Conclusions

There were three main conclusions to the study. First, diagnostic stability was low. Second, stable remission rates were low across all three diagnostic categories, and only 13% of patients had stable remissions. According to the authors, the third finding was the most striking: The overarching diagnosis of an “eating disorder” was relatively stable, while there was considerable change between the three specific eating disorder diagnoses. More than half of the women had a different diagnosis at the end of the 30 months. AN was the most stable diagnosis, followed by BN and EDNOS.

According to Dr. Fairburn and colleagues, the findings highlight certain limitations of the current diagnostic scheme for eating disorders. Minor changes in body weight or eating behavior can result in a person receiving an entirely different DSM-IV diagnosis. The similarities and differences between eating disorder diagnoses and the classification of eating disorders have been discussed for decades. The authors suggest that it might be better to focus upon similarities between the eating disorders categories rather than to stress their differences.

The authors also suggest examining the classification of eating disorders from the perspective of predictive validity. Finally, they suggest that their findings illustrate the clinical reality of shared but distinctive clinical features across the eating disorders, together with flux among them. This flux signifies that common biological and psychological factors may cause and maintain cases of AN, BN, and EDNOS.