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Proposed diagnostic criteria for the DSM-51 include several revisions designed to reduce the preponderance of Eating Disorder Not Otherwise Specified (EDNOS) diagnoses.2 For Anorexia Nervosa (AN), amenorrhea has been eliminated as a requirement. For Bulimia Nervosa (BN), the frequency of recurrent binge-eating episodes and inappropriate compensatory behaviors has been reduced from twice to once per week over the past 3 months. The most dramatic revision involves theformal recognition of Binge ED (BED) as a specified ED.
Proposed changes were based on reviews of the extant literature published within special issues of the International Journal of Eating Disorders toward the end of 2009. Attia and Roberto3 summarized evidence indicating that amenorrhea in AN largely reflects nutritional status, suggesting that amenorrhea is a consequence of AN, similar to changes in blood pressure, body temperature, and bone mineral density, rather than a core feature of the syndrome. Furthermore, this criterion's lack of relevance for men, women taking estrogen, and premenarcheal/postmenopausal women underscored concerns about the feature's clinical utility in defining AN.3 Wilson and Sysko4 summarized evidence calling into question the validity of a twice per week minimum frequency for binge-eating episodes for either BN or BED. Only a handful of studies were available for their review because the twice weekly threshold for binge eating has been present since the DSM-III-R,5 and most studies have used DSM-based criteria in defining EDs. However, data from treatment trials suggested that a once weekly threshold could potentially reduce reliance on EDNOS without altering evidence of treatment efficacy.4 Wonderlich et al.6 reviewed evidence for the validity and clinical utility of BED. Reviewed studies supported the clinical significance of BED and distinctions between BED and AN and BN on course and outcome. In addition, psychological interventions for BED, such as cognitive behavior therapy and interpersonal therapy, demonstrated superiority to behavioral weight loss interventions for treatment of BED, suggesting that there is clinical utility in distinguishing BED from EDNOS in treatment settings.6
Although each proposed revision was based on findings from literature reviews, these findings tend to reflect the influence of changes in isolation. For example, the effect of removing amenorrhea as a criterion for AN is compared to retaining amenorrhea as a criterion rather than in combination with other proposed changes such as reducing the required binge/purge frequency for BN or considering BED as a stand-alone disorder. This reflects, in part, an inability to examine the combined effects of all possible changes before proposed revisions were put forth. However, it remains unclear whether proposed changes will have desired effects on reliance on EDNOS. In addition, it is unclear how the changes, in combination, will influence evidence of validity for diagnostic groupings.
This study compares the DSM-IV and proposed DSM-5 definitions for EDs to evaluate the success of the proposed revisions in reducing reliance on the EDNOS category. In addition, validation analyses are used to compare resulting diagnoses for the extent to which each provides clinically useful information regarding comorbid psychopathology, clinical variables, and treatment history. Data were drawn from an epidemiological study that employed a two-stage design in which structured clinical interviews were used to determine the presence of EDs among those who screened positive for an ED as well as matched controls who screened negative for an ED in the first stage. A significant advantage of this epidemiological study over other, larger and nationally representative studies (e.g., Ref. 7) was the elimination of skip rules in conducting assessments of eating pathology. This allowed comparison of different thresholds for EDs without the constraint of current definitions in detecting EDs.
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The purpose of this study was to compare the DSM-IV diagnostic criteria with those recently proposed for the DSM-5 on number of EDNOS cases and validity. Results indicate that proposed revisions to diagnostic criteria for AN and the addition of BED as a separate diagnostic category will reduce the use of EDNOS among those with a lifetime ED diagnosis. However, proposed revisions to the BN criteria appear to have a very modest influence on use of the EDNOS diagnosis. Validation analyses suggested very little loss of information resulted from proposed revisions.
Given the larger number of DSM-5 groups and resulting decrease in statistical power (particularly for post hoc comparisons), one would predict greater evidence of validity for DSM-IV diagnoses compared to DSM-5 diagnoses even if no true differences existed. However, significant differences emerged in lifetime history of mood and anxiety disorders and GAF scores among ED groups for DSM-5 criteria that were not observed for DSM-IV criteria. Thus, findings suggest slightly improved discrimination among ED groups with the expansion of AN to include those who menstruate and separation of BED from other EDNOS. In addition, comparison of lifetime axis I disorders, clinical features, and treatment history between DSM-IV AN and DSM-5 AN (see Tables 3 and 4) indicates no evidence that the expansion of AN diluted the severity of illness in this group. If anything, remission in the past month decreased, and GAF scores worsened slightly (with slightly decreased standard errors) with the category's expansion.
The limited impact of proposed revisions to the BN diagnostic criteria may reflect the narrow band of individuals who binge and compensate at least once a week but not twice a week over a 3-month period. This finding is consistent with results from a clinic-based sample17 noted by Wilson and Sysko in their review.4 Our review of EDNOS cases that failed to meet the frequency/duration criterion for BN suggest that less conservative adjustments would be required for both the frequency and duration criteria to significantly reduce cases of EDNOS resembling subthreshold BN. However, such changes could result in significant loss of information. In addition to the narrow band of individuals who may be accommodated by proposed changes to BN criteria, some individuals who received a lifetime diagnosis of BN using the DSM-IV criteria were reassigned to lifetime diagnoses of AN due to expansion of the latter group. The overall effect was that the BN group was approximately the same size using DSM-IV or DSM-5 criteria. The similarity in axis I disorders, clinical features, and treatment history for BN defined by DSM-IV versus DSM-5 criteria suggests very little loss of information with proposed revisions.
Finally, the proposed addition of BED resulted in the single largest decrease in EDNOS cases. Validation analyses supported its distinction from other EDNOS on the basis of higher lifetime history of anxiety disorders in BED and detection of a significant difference in lifetime mood disorders between AN and EDNOS after BED was removed from the latter category. The BED group endorsed levels of suicidality that were comparable to those reported by the AN and BN groups (50%, 50%, and 49%, respectively). However, this did not emerge as a significant difference from EDNOS, potentially reflecting limited statistical power for this comparison.
The current results have several clinical implications. First, if the DSM-5 adopts proposed changes to diagnostic criteria for AN and BN, this will result in very little loss of information, consistent with the bases on which changes were proposed.3, 4, 6 For example, the amenorrhea criterion does not appear to add to the concurrent validity of AN diagnoses and thus does not appear to be a valid basis upon which to distinguish between cases of AN and EDNOS. However, clinicians may still be faced with patients who do not meet new criteria for BN because their episodes have persisted for only 2 months or occur less frequently than once per week. This seems particularly likely as treatment history did not distinguish between those with either DSM-IV or proposed DSM-5 diagnoses of BN and EDNOS. Finally, the ability to distinguish individuals with BED from the broader category of EDNOS may help clinicians identify likely differences in comorbid axis I disorders which appear to be lower in EDNOS, once BED is removed. Larger sample sizes are needed to determine whether apparent differences in remission and suicidality also distinguish BED from EDNOS.
This study has some notable strengths and limitations. First, data came from an epidemiological study that used structured clinical interviews but did not adhere to skip rules when assessing eating pathology. Thus, symptom-level ED data were available for all participants. Second, data did not come from treatment-seeking samples which protects against inflated estimates of comorbid axis I disorders18 that could mask potential differences among EDs in comorbidity. Third, stringent alpha values were used to decrease the risk of type I error, and effect sizes were included to allow evaluation of differences that emerged in validation analyses independent of changes related to group size and number. Fourth, this study evaluated a range of variables to establish concurrent validity of diagnoses, including comorbid disorders, GAF, suicidality, remission, and treatment history—all of which represent important clinical indicators.
One limitation is that the sample sizes were not large enough to detect small effect sizes for group comparisons, which contributed to restricted statistical power during pairwise comparisons of groups with post hoc-corrected p values. Relatedly, we did not examine AN and BN subtypes in migration or validation analyses given that this approach would have further reduced group sizes. Given the proposal to eliminate the nonpurging subtype of BN, this is an important topic for future investigations. In addition to not evaluating proposed changes in subtypes, we were unable to evaluate the influence of proposed clarifications in the wording of certain AN criteria. For example, the proposed change for criterion A of AN does not present an alternative weight threshold that we could evaluate. Moreover, this criterion may be established using the example threshold provided in the DSM-IV (as we did in our analyses), using a less stringent threshold, or using a more stringent threshold. Similarly, we were unable to reconstruct from interviews “persistent behavior to avoid weight gain” (proposed revision to criterion B of AN as an alternative to explicit endorsement of intense fear of gaining weight or becoming fat). Thus, our estimate of the increase in AN diagnoses with proposed DSM-5 criteria is likely to be conservative. Finally, our validation analyses focused exclusively on variables that represent concurrent validity—that is, assessment of other lifetime variables assessed concurrently with assessment of lifetime ED diagnoses. Future studies should examine whether proposed changes influence evidence of etiologic and predictive validity.19
Overall, findings support proposed revisions toEDs in the DSM-5 as successfully reducing reliance on EDNOS without significant loss of information. The most controversial change, introduction of BED, did not result in an abundance of this diagnosis in this community-based sample. Moreover, proposed revisions reflect a fairly conservative approach to changing ED definitions similar to that employed in revising previous editions of the DSM. The key advantage of this conservative approach, as evidenced by the current findings, is very little loss of information. The key disadvantage is that it appears likely that EDNOS may continue to be the most common diagnosis, particularly in community-based samples. However, proposals to include specific, named alternative forms of EDNOS in the DSM-5,1 such as purging disorder and night eating syndrome, may pave the way for continued progress in future editions of the DSM.