From a cohort of more than 13.5 million people who were born or lived in Sweden between 1969 and 2009, Mataix-Cols et al. [7] found that the FDRs of the 24,768 individuals with OCD were more likely to also have OCD (OR = 5.03, 95% CI = 4.49–5.64 for siblings; OR = 4.70, 95% CI = 4.09–5.40 for parents; and OR = 4.56, 95% CI = 3.97–5.24 for the offspring); that this risk decreased proportionally to the degree of genetic relatedness; and that the risk tended to be higher amongst FDR of early-onset OCD individuals.
