Probabilistic reasoning in patients with body dysmorphic disorder

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).

Participants completed a clinician-rated measure of delusionality and two tests of probabilistic reasoning: the beads task and the survey task.

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.

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.

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.