An evaluation of the enhanced cognitive-behavioural model of bulimia nervosa

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Abstract

The original cognitive-behavioural model of bulimia nervosa (BN) has been enhanced to include four additional maintaining mechanisms: low self esteem, clinical perfectionism, interpersonal problems, and mood intolerance. These models have been used to guide cognitive-behavioural treatment for BN, but the enhanced model has yet to be directly evaluated as a whole in a clinical sample. This study aimed to compare and evaluate the original and the enhanced cognitive-behavioural models of BN using structural equation modelling. The Eating Disorder Examination and self-report questionnaires were completed by 162 patients seeking treatment for BN (N = 129) or atypical BN (N = 33). Fit indices suggested that both the original and enhanced models provided a good fit to the data, but the enhanced model accounted for more variance in dietary restraint and binge eating. In the enhanced model, low self esteem was associated with greater overevaluation of weight and shape, which, in turn, was associated with increased dietary restraint. Interpersonal problems were also directly associated with dietary restraint, and binge eating was associated with increased purging. While the current study provides support for some aspects of the enhanced cognitive-behavioural model of BN, some key relationships in the model were not supported, including the important conceptual relationship between dietary restraint and binge eating.

Highlights

► Both cognitive-behavioural models of bulimia nervosa provided a good fit to the data. ► The enhanced model accounted for more variance in dietary restraint and binge eating. ► The relationship between dietary restraint and binge eating was not supported.

Section snippets

Participants and procedures

Participants were female patients with an eating disorder who were referred and assessed for treatment at an outpatient mental health service in Perth, Western Australia. Data were collected upon initial presentation as part of a larger assessment protocol between April 2005 and November 2010. Height and weight were measured during the initial assessment to obtain body mass index (BMI; weight/height2). The Eating Disorder Examination (EDE; Fairburn & Cooper, 1993) was administered to determine

Preliminary data analysis

Missing data were observed for 11 cases (15 missing values in total), and were imputed using expectation–maximisation in SPSS. No missing data were observed on key outcome variables (e.g., binge eating, purging).

Histograms of model variables were inspected for normality. The distribution of binge eating and purging was suggestive of substantial positive skew. Binge eating and purging variables were transformed using square root transformation, which substantially reduced the skew statistics.

Discussion

This study aimed to evaluate the original and enhanced CB-BN models with a sample of patients seeking treatment for BN or atypical BN. Goodness-of-fit indices suggested that both the original and enhanced models of BN provided a good fit to the data, and both models accounted for a similar proportion of variance in purging. However, results indicated that the enhanced model accounted for a greater proportion of variance in dietary restraint and binge eating than the original model. This

Acknowledgements

Ms Lampard acknowledges the support of the Butterfly Foundation, a UWA Convocation Travel Award, and a UWA Completion Scholarship.

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