The primary aim of this study was to compare the course and stability of EDNOS compared with AN, BN, and BED. As a recent comprehensive review of the literature pointed out “virtually nothing is known about the persistence of EDNOS” (20
). Yet, as many authors have noted EDNOS comprises the largest ED group, has similar psychopathology to other eating disorders particularly BN, and is accompanied by considerable disability (1
). In this study we constructed an EDNOS group from the partial syndromes of AN, BN, and BED, hence the subcomponents of EDNOS as defined in could be examined individually.
The first question posed concerned the course of EDNOS. Hence we examined time to first remission from entry to the study. There was a significant difference in time to first remission among the four syndromes with EDNOS and BED showing the shortest and almost identical times, and BN showing the longest time followed by AN. Nearly 80% of the EDNOS group had no ED at the 4-year follow-up with a similar figure for BED. Next, time from first remission to relapse to any ED diagnosis was examined. No significant differences were found among the four groups in this analysis. Overall, these findings are similar to those of previous studies, i.e. EDNOS remits more quickly and has a higher rate of recovery over time than AN or BN (7
). However, in the present study no differences in course were found between EDNOS and BED. As found in other studies the majority of cases from all the ED syndromes no longer have their original diagnosis at the end of the 4-year follow-up (11
We next examined the time to remission and to first relapse following remission for the three subcomponents (PAN, PBN, PBED) of EDNOS. There were no statistically significant differences among these subcomponents for either time to remission or time to first relapse, suggesting identical courses.
With the exception of EDNOS as shown in , there are few transitions from one eating disorder to another with most transitions occurring between AN and BN. These findings suggest that EDNOS is mainly composed of individuals with an ED diagnosis transitioning to no diagnosis or from no diagnosis to an eating disorder diagnosis. It is noteworthy that few individuals transition directly on average over a 6-month time interval from a full eating disorder diagnosis to no diagnosis. A retrospective study of the EDNOS group found that the majority had a full ED in the past. This is consistent with the prospective finding that patients with a full ED transition to remission via EDNOS. In addition only 18% of the EDNOS group without a full ED diagnosis recovered without developing another ED or persisted as EDNOS. However, this “pure” EDNOS group did not differ from the remaining EDNOS group in terms of times to remission or relapse or on any baseline characteristic.
Despite the strengths of this study, namely its prospective nature, frequent assessment by standard interview, and fairly large sample size, there are some limitations that need to be taken into account. The majority of participants received some form of treatment during the follow-up period specifically directed at their eating disorder. Although the proportions of individuals treated as outpatients were similar for the four groups, hospitalization was more frequent for AN than for the other groups possibly differentially affecting the course of this syndrome. It is probable that without specific ED treatment the outcome of these disorders, particularly for AN, would have been worse. In addition, the number of participants with AN is relatively small. However, given the frequency of some form of treatment for eating disorders found in this and other studies (6
) it is unlikely that a prospective study would be able to follow an untreated cohort over time. Finally, the EDNOS group was composed of partial cases of AN, BN, and BED omitting other syndromes that now populate EDNOS such as night eating syndrome, and purging syndrome (4
). However, the majority of EDNOS cases appear to be subclinical variants of the three main ED’s (4
In conclusion, the results of this study suggest that EDNOS is a way-station for those moving from a full ED or from remission to another ED. The retrospective examination of the EDNOS group found that the majority had a full ED diagnosis in the past and that there are few true EDNOS cases. It is likely that the composition of EDNOS will vary with the age of the cohort. For example, in adolescence it may be that a higher proportion of cases would be on the path toward a full ED syndrome.
These results may have implications for DSM-V and for the problematic diagnostic category of EDNOS (2
). Given that EDNOS is largely a transient category it may make sense to use that diagnosis only for cases that have never met criteria for a full ED. For example, a patient with AN who transitions to another ED diagnosis including EDNOS should continue to be diagnosed as having AN. This would remove the majority of diagnoses from the EDNOS category to a full ED syndrome leaving only those who have not yet met lifetime criteria for a full ED diagnosis and those with as yet undefined syndromes as EDNOS cases.