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.