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Binge eating is a cardinal criterion for the diagnosis of bulimia nervosa (BN) and the provisional diagnosis of binge eating disorder (BED),1 but it is also reported by individuals with anorexia nervosa (AN) of the binge-eating/purging type (AN-BP).1
According to the DSM-IV-TR, an episode of binge eating is characterized both by eating an amount of food that would normally be regarded as too large, and by a sense of lack of control over eating.1 Unfortunately, there are no specific guidelines regarding the threshold of the amount of food necessary to satisfy the inclusion in the AN-BP type. This causes difficulties in classifying AN-BP, especially when clinicians see underweight patients who report regular episodes of loss of control over eating but do not have regular episodes of purging. In addition, individuals with eating disorders may fail to identify the binge episodes on the basis of food amount, giving greater emphasis to the loss of control than to the amount of food in their definition of binge eating.2, 3
The evidence supporting the validity of the DSM-IV-TR definition of binge eating as this applies to BN and variants of BN is limited.4–6 In patients with BN, “objective” and “subjective” bulimic episodes, as defined according to the Eating Disorder Examination (EDE),7 seem to be associated with a similar severity of clinical impairment and/or other clinical data (e.g., psychopathology, past-history of AN, psychiatric symptoms, interpersonal distress, low self-esteem and self-efficacy, and social adjustment).8 Other clinical studies confirmed that objective and subjective bulimic episodes are associated with similar levels of depression or anxiety,9, 10 and that the age of onset and the predictors of the two types of bulimic episodes are almost identical,11 while their frequency is different.12 Findings from community-based studies similarly suggest that individuals with bulimic-type eating disorders who report objective bulimic episodes are similar, in terms of eating disorder and comorbid psychopathology, to those who report subjective bulimic episodes.13–15
The possible effects of the type and frequency of bulimic episode on treatment response have rarely been considered. The limited data available have suggested that subjective episodes remit more slowly in patients with BED16 and both persist at the end of treatment in patients with BN.17 Subjective episodes did not respond well to self-monitoring in women with either BN or BED,18 whereas this strategy was effective in reducing objective episodes.19 As to the influence on treatment outcome, only the presence of subjective episodes predicted the response to placebo in participants with BED.20
As pointed out in a recent review,6 no meaningful information has ever been reported on the binge eating episodes in underweight ED-NOS and AN. Limited information is also available on the personality characteristics of the underweight individuals with different types of bulimic episodes and on their role on treatment response, a key aspect to define the clinical utility of a DSM diagnosis.21 The goal of this study was, therefore, to investigate the psychopathological features associated with objective and subjective bulimic episodes in underweight individuals with eating disorder, and to test their role on treatment outcome.
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In an inpatient CBT unit for eating disorder, we identified three groups of underweight patients who reported regular objective bulimic episodes with or without subjective bulimic episodes (OBE group), regular subjective bulimic episodes only (SBE group) and neither objective nor subjective bulimic episodes (no-RBE group). These groups were assessed on a wide range of outcomes before and after treatment, including, age, age of menarche, BMI, premorbid BMI, eating disorder duration, suicidal attempts, eating disorder psychopathology, general psychopathology, personality characteristics, and treatment outcome. The main findings were twofold. First, in terms of eating disorder and comorbid psychopathology at baseline, similarities between the OBE and SBE groups outweighed the differences, whereas differences between these groups and the no-RBE group were more pronounced. Second, all three groups had similar outcomes in response to inpatient CBT.
At baseline, our underweight OBE, SBE, and no-RBE groups had similar sociodemographic and clinical characteristics and severity of general psychopathology, also including similar suicidal attempts, thus confirming previous studies in non-underweight clinical8–11 and community samples with objective and subjective bulimic episodes.5, 13, 14 The OBE group had significantly higher BMI than the SBE and no-RBE groups, a finding reported previously in relation to individuals with bulimic-type eating disorders,5, 15 and a higher number of episodes of self-induced vomiting, a difference not observed, to our knowledge, among individuals with bulimic-type eating disorders.5 These findings might be seen to be consistent with the view that purging behaviors are inefficient as means of reducing caloric intake.38
The OBE and SBE groups were characterized by more severe eating disorder psychopathology, in particular significantly higher eating concern and lower self-directness at TCI, a finding also observed in a previous study on AN subtypes,39 than the no-RBE group. According to Cloninger et al.,40 self-directedness is a developmental process encompassing several distinct aspects, including acceptance of responsibility for one's choices, identification of individually valued goals and purposes, resourcefulness, and self-acceptance. Lower self-directness, has been observed associated with poor outcome in patients with eating disorder,41 and with higher drop-out rates in patients with AN treated with brief outpatient individual psychodynamic therapy.42
Importantly, however, in this study the three groups had a similar dropout rate and time to dropout, and responded similarly well to the inpatient CBT, with a significant improvement of BMI, eating disorder behaviors, eating disorder and general psychopathology, and of several personality features (namely, increased self-directness—a prognostic indicator of treatment efficacy—43 and harm avoidance, and decreased persistence and self-transcendence). By the end of treatment, all groups had achieved a mean normal BMI, but the no-RBE group was more prone to regaining weight. This latter finding suggests that there may be limited clinical utility in categorizing underweight eating disorder patients on the basis of the type or frequency of bulimic episodes.
In regression analysis, a higher frequency of subjective bulimic episodes and of episodes of intense exercising prior to admission was associated with a lower reduction in eating disorder psychopathology following treatment, after controlling for initial BMI, age, frequency of self-induced vomiting, laxative and diuretic misuse, and exercising. In contrast, the frequency of objective bulimic episodes prior to admission was not independently associated with any change in eating disorder symptoms following treatment. According to these data, specific strategies should be developed to address subjective bulimic episodes and intense exercising, to improve the outcome of our CBT-based inpatient treatment.
The strengths of the study are the inclusion of several ED-NOS cases, a group scarcely evaluated in previous research on bulimic episodes, and the assessment of bulimic episodes using the accurate EDE interview before and after treatment,8 but several limitations should be also noted. First, because of the limited sample size we could not split our OBE group according to the presence/absence of subjective bulimic episodes as used in other studies.5 The preliminary analysis within the OBE group, showed a higher eating concern in patients with subjective bulimic episodes which may be partly explained by the loss of control over eating that characterizes both OBE and SBE patients. However, no other significant differences emerged between the two groups at baseline. Second, sample size precluded a more stringent separation of “regular binge eating” (“once a week or more”) from “nonregular binge eating” (“less than once a week”) when assigning participants to groups. This may have had the effect of minimizing differences between groups. Although the once a week threshold has been recently shown to capture individuals with clinically significant levels of binge eating psychopathology,27, 28 our definition might have minimized differences between groups. Third, data were derived from a single inpatient unit, mainly treating adult underweight patients; external validation is needed, and the results might not apply to underweight outpatients or adolescent subjects or to individuals with AN- or AN-type EDNOS receiving inpatient treatment in other regions. Fourth, life-time history data on objective and subjective bulimic episodes were not fully available, and the possible effects of crossover between the two types on outcome cannot be evaluated. Fifth, the lack of follow-up precludes any inference on the long-term outcome of patients with OBE and SBE.
In conclusion, our data show that underweight eating disorder patients have similar treatment response to an intensive inpatient program of CBT regardless of whether or not they report objective and/or subjective bulimic episodes. Although methodological limitations preclude any firm conclusions, the findings suggest that there may be limited clinical utility in categorizing underweight eating disorder individuals on the basis of the type and frequency of bulimic episodes and that further investigation of the validity of distinguishing OBE and SBE among underweight eating disorder patients is warranted. Finally, greater attention may need to be given to the role of SBE and excessive exercise in improving treatment outcome for individuals with AN and variants of AN.