The cognitive-behavioural theory and treatment for eating disorders and disordered eating: A direct evaluation

In a series of four studies, the aim of the current research project was to evaluate the cognitive-behavioral theory and treatment (CBT) of eating disorders. The first study (Chapter 5) was a meta-analysis (Linardon, Wade, De la Piedad Garcia, & Brennan, in press) of randomized controlled trials (RCT) testing the efficacy of CBT for eating disorders. Pooling data from 79 RCTs, results showed that therapist-led and guided self-help CBT were efficacious for individuals with bulimia nervosa (BN) and binge eating disorder (BED). There was no evidence to suggest that CBT was more efficacious than other psychological interventions in anorexia nervosa (AN).

Having found evidence supporting the efficacy of CBT for certain eating disorder presentations, the second study (Chapter 6), which was a systematic review, focused on identifying the reliable factors that mediate, moderate, or predict outcome during CBT (Linardon, de la Piedad Garcia, & Brennan, 2016b). This review found that mediators and moderators of change have been largely unexplored, and that no reliable predictors of outcome emerged. Therefore, based on existing evidence, it was concluded that it remains unclear how, for whom, and under what conditions, CBT for eating disorders works.

To understand the mechanisms through which CBT for eating disorders may work, a cross-sectional evaluation of the cognitive-behavioral model in a large non-clinical sample was employed for the third study (Chapter 8; under review). This study validated the conceptual pathways hypothesized by the cognitive model; it also identified two additional variables that might be important mechanisms of change during CBT, body checking and dichotomous thinking. The inclusion of body checking and dichotomous thinking within the cognitive-behavioral model explained nearly three times the amount of variance in disordered eating symptoms than the model without these variables. The third study offered the necessary statistical support for the cognitive-behavioral model and its hypotheses.

The final study (Chapter 10) utilized a single case experimental design (n=8) to test the hypothesized cognitive-behavioral mechanisms of change during a CBT guided self-help program. The potential mechanisms of change examined were shape and weight concerns, dietary restraint, and adherence to regular eating strategies. Preliminary evidence showed that an adherence to regular eating in the second week of CBT was associated with a concurrent decrease in dietary restraint and binge eating. From this study, there was no evidence that other potential mechanisms were operating to reduce binge eating behavior.

Based on these four independent research studies, this thesis gathered converging evidence in support for the underling cognitive-behavioral model of eating disorders. Further, these findings suggest that CBT for eating disorders is likely to contain several theory-specific mechanisms that are responsible for this treatments effectiveness. More broadly, the current thesis offers support for the contention that CBT for eating disorders “works” because of the reason outlined by its underlying model and because of its specific therapeutic mechanisms.