Insight impairment in body image disorders: delusionality and overvalued ideas in anorexia nervosa versus body dysmorphic disorder

The two body image disorders anorexia nervosa (AN) and body dysmorphic disorder (BDD) share many similarities. Delusionality in BDD has recently gained increased attention, as the new DSM-5 criteria for BDD include an insight specifier. However, delusionalilty in AN has rarely been examined. We evaluated the delusionality of appearance-related beliefs in AN (n=19) vs. BDD (n=22) via structured interview. Participants also completed measures of disorder-specific psychopathology and body image. Compared to those with AN, individuals with BDD exhibited significantly greater delusionality on a dimensional scale (p=0.0014, d=1.07), and were more likely to meet dichotomous criteria for delusional beliefs (p=0.021, V=0.36). In AN, delusionality was associated specifically with shape concerns and drive for thinness; in BDD, delusionality was related to the severity of BDD symptoms (all p<0.05). Delusionality of appearance beliefs is present in individuals with AN, but is less pronounced than in BDD. Nevertheless, as high delusionality might predict poor treatment outcome in AN, treatment strategies that were originally developed to address delusionality in BDD might be modified for AN.