Brain structure and circuitry in body dysmorphic disorder (BDD) patients: a multimodal neuroimaging study

Body dysmorphic disorder (BDD) is a mental disorder with five times the prevalence of anorexia, affecting up to 2.4% of the general population. The main symptom is a fixation on a feature of appearance that they attest looks ugly and they may engage in repetitive and ritualistic behaviour, including picking of their skin or checking their appearance in the mirror very frequently. The concern with appearance and associated behaviours are analogous to the obsessions and compulsions experienced in obsessive compulsive disorder (OCD). This thesis aimed to characterise the brain structure and circuitry of BDD to understand the mechanism that underlie the disorder's onset and maintenance. We acquired the largest BDD neuroimaging sample to date, scanning 20 BDD participants and compared them to 20 healthy controls. Three imaging techniques were reported; structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI) and resting state functional MRI. The structural data showed reduced volumes in the orbitofrontal and anterior cingulate cortex, while the DTI data revealed for the first time that BDD patients have compromised integrity of most major white matter tracts throughout the brain. Resting state functional MRI showed abnormalities in fronto-amygdala and occipital lobe connectivity. Collectively, our evidence contributed rich data showing widespread abnormalities in the brains of BDD participants. These abnormalities may be the foundation for BDD symptoms, including increased fearful threat perception, and dysfunction in self-reflection, executive function and visual processing. It was concluded that the frontal and fronto-amygdala deficits found in BDD are important to the disorder, and suggest it lies on a spectrum of anxiety disorders characterized by emotional dysregulation.