Thought-Shape Fusion in bulimia nervosa: an experimental investigation.

The aim of the present study was to experimentally investigate a cognitive distortion, 'Thought Shape Fusion' (TSF), in patients with bulimia nervosa (BN). TSF has been postulated as a specific distortion in patients with eating disorders and occurs when the thought about eating a forbidden food increases a person's estimate of her weight / shape, elicits a perception of moral wrongdoing and makes her feel fat. Previous psychometric measures of TSF in clinical and control groups, experiments eliciting TSF in a student sample and in patients with anorexia nervosa, all confirm a strong association between TSF and eating disorder psychopathology. Twenty patients diagnosed with BN participated in a within-participants experimental design with the aim of eliciting TSF and investigating further the possible effects of corrective behaviours (checking and mental neutralizing). Verbal analogue scales constituted the main outcome measures. TSF triggered a perception of moral wrongdoing, heightened levels of body dissatisfaction, elevated feelings of anxiety and guilt and prompted urges to engage in checking and mental neutralizing. Corrective behaviours significantly reduced the effects of the experimental procedure. Components of TSF are present in BN and are likely to play a mediating role in the maintenance of the disorder. The precise connection between TSF and BN remains to be explored in future clinical trials.