Empirical evidence for cognitive subgroups in body dysmorphic disorder.

OBJECTIVE: Current understanding of cognitive functioning in body dysmorphic disorder is limited, owing to few studies, small sample sizes and assessment across only limited cognitive domains. Existing research has also shown inconsistent findings, with both intact and impaired cognition reported in body dysmorphic disorder, which might point towards cognitive heterogeneity in the disorder. This study aimed to examine the cognitive profile of body dysmorphic disorder in a large sample across eight cognitive domains, and to explore whether cognitive subgroups might be identified within body dysmorphic disorder. METHOD: Cognitive domains of inhibition/flexibility, working memory, speed of processing, reasoning and problem-solving, visual and verbal learning, attention/vigilance and social cognition were assessed and compared between 65 body dysmorphic disorder patients and 70 healthy controls. Then, hierarchical clustering analysis was conducted on the body dysmorphic disorder group's cognitive data. RESULTS: Group-average comparisons demonstrated significantly poorer cognitive functioning in body dysmorphic disorder than healthy controls in all domains except for attention/vigilance and social cognition. Cluster analysis identified two divergent cognitive subgroups within our body dysmorphic disorder cohort characterised by (1) broadly intact cognitive function with mild selective impairments (72.3%), and (2) broadly impaired cognitive function (27.7%). However, the clusters did not significantly differ on clinical parameters or most sociodemographic characteristics. CONCLUSION: Our findings demonstrate considerable cognitive heterogeneity among persons with body dysmorphic disorder, rather than uniform deficits. Poor performances in the broadly impaired subgroup may have driven group-level differences. However, our findings also suggest a dissociation between cognitive functioning and clinical characteristics in body dysmorphic disorder that has implications for current aetiological models. Additional research is needed to clarify why some people with body dysmorphic disorder demonstrate cognitive deficits while others do not.

The neurobiology of body dysmorphic disorder: A systematic review and theoretical model.

There has been an increase in neuroimaging research in body dysmorphic disorder (BDD), yet little is known about the underlying neurobiological basis of the disorder. We aimed to provide a systematic overview of the literature on the neurobiology of BDD. Two reviewers undertook a search of three electronic research databases: PubMed, PsycINFO, and Google Scholar. The search consisted of synonyms commonly associated with BDD and methods to evaluate brain structure, function, and network organisation. Out of an initial yield of 175 articles, 19 fulfilled inclusion criteria and were reviewed. We identified differences in brain activity, structure, and connectivity in BDD participants in frontostriatal, limbic, and visual system regions when compared to healthy control and other clinical groups. We put forth a neurobiological model of BDD pathophysiology that involves wide-spread disorganisation in neural networks involved in cognitive control and the interpretation of visual and emotional information. This review considers how this model might aid in the development of future research and understanding of BDD.

Is body dysmorphic disorder associated with abnormal bodily self-awareness? A study using the rubber hand illusion.

Evidence from past research suggests that behaviours and characteristics related to body dissatisfaction may be associated with greater instability of perceptual body image, possibly due to problems in the integration of body-related multisensory information. We investigated whether people with body dysmorphic disorder (BDD), a condition characterised by body image disturbances, demonstrated enhanced susceptibility to the rubber hand illusion (RHI), which arises as a result of multisensory integration processes when a rubber hand and the participant's hidden real hand are stimulated in synchrony. Overall, differences in RHI experience between the BDD group and healthy and schizophrenia control groups (n = 17 in each) were not significant. RHI strength, however, was positively associated with body dissatisfaction and related tendencies. For the healthy control group, proprioceptive drift towards the rubber hand was observed following synchronous but not asynchronous stimulation, a typical pattern when inducing the RHI. Similar drifts in proprioceptive awareness occurred for the BDD group irrespective of whether stimulation was synchronous or not. These results are discussed in terms of possible abnormalities in visual processing and multisensory integration among people with BDD.

An investigation of a novel transdiagnostic model of delusions in a group with positive schizotypal symptoms.

INTRODUCTION: Although several theories of delusions have been put forward, most do not offer a comprehensive diagnosis-independent explanation of delusion aetiology. This study used a non-clinical sample to provide empirical support for a novel transdiagnostic model of delusions that implicates aberrant semantic memory and emotion perception processes as key factors in delusion formation and maintenance. It was hypothesised that among a non-clinical sample, people high in schizotypy would demonstrate differences in semantic memory and emotion perception, relative to people low in schizotypy. METHODS: Using the Cognitive Disorganisation subscale of the Oxford-Liverpool Inventory of Feelings and Experiences, 41 healthy participants were separated into high and low schizotypy groups and completed facial emotion perception and semantic priming tasks. RESULTS: As expected, participants in the high schizotypy group demonstrated different performance on the semantic priming task and reduced facial affect accuracy for the emotion anger, and reaction time differences to fearful faces. CONCLUSION: These findings suggest that such processes may be involved in the development of the sorts of unusual beliefs which underlie delusions. Investigation of how emotion perception and semantic memory may interrelate in the aetiology of delusions would be of value in furthering our understanding of their role in delusion formation.

Own-body perception in body dysmorphic disorder.

INTRODUCTION: This paper reviews the literature as it relates to perceptual processes in body dysmorphic disorder (BDD). METHODS: A narrative-style review of the literature was undertaken to explore the relationship between BDD and obsessive-compulsive disorder, the empirical evidence for aberrant own-body perception in BDD, and the possible role of the parietal cortex in the disorder. RESULTS: The extant literature appears to support the postulation that BDD is underpinned by a dysfunction in somatoperception-the process by which individuals formulate a sense of what they look like. CONCLUSIONS: Investigation of somatoperceptive processes in BDD and related brain structures would provide important insight about the development and maintenance of this complex and often neglected psychiatric condition, and, in turn, help improve its treatment.