PROVIDENCE – The criteria used to diagnose common eating disorders are insufficiently broad, causing most patients to receive an “NOS” diagnosis, researchers from Rhode Island Hospital and Brown University say in a report published today in the online edition of the Journal of Clinical Psychiatry.

The report – from the Rhode Island Hospital Methods to Improve Diagnostic Assessment and Services (MIDAS) Project – notes that bulimia and anorexia nervosa are the only two eating disorders officially defined by the American Psychiatric Association in its Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, although an appendix to the DSM-IV states that binge-eating disorder may be included in the next edition.

But in treatment-center programs for eating disorders, more than half of patients are diagnosed with an eating disorder “not otherwise specified” (NOS), the researchers found.

“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,” said Dr. Mark Zimmerman, the director of outpatient psychiatry at Rhode Island Hospital and an associate professor of psychiatry and human behavior at Brown’s Warren Alpert Medical School. He is the MIDAS project’s principal investigator and the new study’s lead author.

“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 said. “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 sub-threshold variants.”

The study examined 330 patients diagnosed with a lifetime history of an eating disorder.

Of those patients, 307 were diagnosed with one disorder apiece and 23 with two disorders. Nearly half the patients (164) had a current eating disorder; nearly one in five (60) had an eating disorder in partial remission; and more than one in three (129) had a past disorder, the study found.

Among those with current eating disorders, the study found, the most common diagnoses were NOS (84) and binge-eating disorder (64), which together comprised 148 of the 164 current diagnoses. Of those 84 patients with current NOS diagnoses, most were diagnosed as “not otherwise specified” because they fell below the threshold of the three recognized disorders, the researchers said: “More than half … could be considered sub-threshold anorexia nervosa (20.2 percent), sub-threshold bulimia nervosa (20.2 percent) and sub-threshold binge eating disorder (32.1 percent).”

Rhode Island Hospital, a private nonprofit institution founded in 1863, is a founding member of the Lifespan health system and the largest teaching hospital for The Warren Alpert Medical School of Brown University. Additional information is available at www.rhodeislandhospital.org . To learn more about the MIDAS Project, visit www.lifespan.org.