Probabilistic reasoning in patients with body dysmorphic disorder.

BACKGROUND AND OBJECTIVES: Many patients with body dysmorphic disorder (BDD) have poor insight into their condition. Indeed, their conviction in their ugliness is often delusional. Perhaps the most robust information-processing abnormality associated with delusions is a jumping to conclusions (JTC) reasoning bias such that delusional individuals request significantly less information before making a decision relative to healthy controls. We investigated whether patients with BDD (n = 20) demonstrate a JTC reasoning style relative to patients with OCD (n = 20) and healthy controls (n = 20).
METHODS: Participants completed a clinician-rated measure of delusionality and two tests of probabilistic reasoning: the beads task and the survey task.
RESULTS: Patients with BDD did exhibit higher delusionality than the patients with OCD. They did not, however, exhibit a JTC reasoning bias relative to the patients with OCD or the healthy controls. Patients with poor insight BDD requested significantly less information before making a decision than did patients with fair insight BDD. LIMITATIONS: The clinical groups were characterized by multiple comorbidities and concomitant medications. The BDD group had relatively good insight as compared to other studies examining delusionality in BDD.
CONCLUSIONS: Taken together, our results suggest that although a JTC reasoning bias was not present in all patients with BDD, a modest JTC reasoning bias may be present among patients with poor insight BDD. Future studies could provide additional information on this hypothesis.