A new study finds medical labeling of eating disorders is inadequate as a majority of patients do not fit the diagnostic criteria for bulimia and/or anorexia nervosa.
As a consequence, individuals are diagnosed with an eating disorder “not otherwise specified” (NOS). This classification is seen as too vague leading to difficulty in tracking prevalence of the condition and assessing the success of various treatment strategies.
In the current DSM-IV manual, bulimia and anorexia nervosa are the only officially recognized and formally defined eating disorders. A third, binge eating disorder, is listed in the Appendix as a disorder requiring further study for possible inclusion in the next edition.
Researchers noted that in treatment center programs for eating disorders more than half of the patients are diagnosed with an eating disorder “not otherwise specified” (NOS). The researchers anticipated that in a general psychiatric setting, patients’ conditions would be less severe than in a specialized center.
The Rhode Island Hospital study looked at 330 patients who were diagnosed with a lifetime history of an eating disorder. Of those, 307 received 1 diagnosis and 23 were diagnosed with 2 disorders. The majority of the patients (85 percent) were female with a mean age of 34.3 years.
Of the 330 patients, almost half (164) had a current eating disorder, 60 had an eating disorder in partial remission and slightly more than one-third (129) had a past diagnosis.
Lead author Mark Zimmerman, M.D. said, “The NOS category of the DSM-IV was intended to be a residual category of diagnosis to provide a diagnostic option for relatively infrequent cases. This study has shown that eating disorder NOS cases predominate and suggests a problem with the DSM-IV nomenclature for this class of disorders.”
Zimmerman also noted, “Our study and its results are consistent with other studies suggesting that the criteria for anorexia, bulimia and binge eating disorder should be broadened to include subthreshold variants.”
The study found the most frequent current eating disorder diagnoses were NOS and binge eating disorder (148 of the 164 current diagnoses). Researchers also found that of those 84 patients with a current eating disorder diagnosed as NOS, more than half those patients could be considered subthreshold anorexia nervosa (20.2 percent), subthreshold bulimia nervosa (20.2 percent) and subthreshold binge eating disorder (32.1percent). They were diagnosed NOS because they fell below the threshold of one of the three DSM-IV defined eating disorders.
When binge-eating disorder was combined with other forms of eating disorder NOS, as it is in DSM-IV, 90.2 percent of the patients with a current eating disorder were diagnosed with eating disorder NOS.
The report is from the Rhode Island Hospital Methods to Improve Diagnostic Assessment and Services (MIDAS) Project, for which Zimmerman is the principal investigator.
The MIDAS project examined 2,500 patients in an outpatient psychiatric practice using a comprehensive diagnostic evaluation. Zimmerman said, “The MIDAS project is unique in its integration of research quality diagnostic methods into a community-based outpatient practice affiliated with an academic medical center.”