A Population-Based Family Clustering Study of Body Dysmorphic Disorder

Body dysmorphic disorder (BDD) is a debilitating and understudied psychiatric condition of largely unknown etiology. Emerging evidence suggests that BDD may be a familial and heritable disorder, but family studies of diagnosed individuals and their biological relatives are yet to be conducted.

We identified 4,857,049 individuals born in Sweden between 1960 and 2008 with information on both biological parents who were living in Sweden in 1997. From this cohort, we identified clusters of full siblings, half siblings, and cousins and compared the risk of BDD among those with a relative diagnosed with BDD and those without. Previously validated ICD-10 diagnoses of BDD were identified through the Swedish National Patient Register. To estimate hazard ratios (HRs), we fitted a series of Cox regression models with time-varying exposures and attained age as the underlying time scale. Individuals were considered unexposed before their relative's BDD diagnosis and exposed thereafter.

Relatives of individuals with BDD had a higher risk of BDD compared with relatives of individuals without BDD, with the highest risk observed in full siblings (HR, 16.2; 95% CI, 9.2-28.7), followed by half-siblings (HR, 7.8; 95% CI, 2.5-23.9) and cousins (HR, 2.8; 95% CI, 1.3-6.2), showing a gradient by degree of genetic relatedness.

Our findings indicate that BDD is a familial disorder and suggest an important role for genetic factors.