Title: Delusional beliefs in individuals with Body Dysmorphic Disorder
Description: Individuals with Body Dysmorphic Disorder (BDD) suffer from a distressing preoccupation with imagined or very slight defects in their physical appearance. Most have very poor insight into their disorder. Indeed, their conviction in their ugliness is often of delusional intensity. Despite this finding, very little research has examined whether BDD patient exhibit other symptomatic and/or cognitive vulnerabilities to psychosis. In this dissertation, I explore the degree to which individuals with BDD (n = 20) demonstrate elevated psychosis-proneness and/or cognitive features that have been linked to delusion formation relative to individuals with Obsessive Compulsive Disorder (OCD; n = 20) and healthy controls (n = 20). Specifically, I examined whether individuals with BDD exhibit higher levels of delusional ideation, schizotypy, or both relative to the other two groups. I also examined one perceptual process, symmetry detection, and two higher-level processes: probabilistic reasoning and reality monitoring. I hypothesized that performance on all three of these processes would be aberrant among the BDD patients relative to the other two groups.

The BDD patients exhibited higher delusionality regarding their primary disorder- related belief and higher levels of delusional ideation relative to the OCD patients and healthy controls. The BDD and OCD patients exhibited higher levels of schizotypy relative to the healthy controls, but did not differ from one another. The BDD group was not better or faster at detecting differences in facial symmetry relative to the OCD patients and the healthy controls. The BDD patients also did not exhibit a reasoning bias relative to the OCD patients and the healthy controls. However, BDD patients with poor insight exhibited a reasoning bias relative to the BDD patients with fair insight. The BDD patients did not exhibit a deficit in reality monitoring ability relative to the OCD patients and the healthy controls. Taken together, the results of this dissertation send a consistent message regarding delusionality in BDD. Patients with BDD may be slightly elevated on the continuum of psychosis relative to individuals with OCD and healthy controls, but they are still a far cry from individuals with a psychotic disorder.