Normative childhood repetitive routines and obsessive compulsive symptomatology in 6-year-old twins

Background: To investigate the association between normative repetitive routines of childhood and paediatric obsessive compulsive symptom syndrome (OCSS) and the extent to which it is genetically mediated. Methods: In a two-phase design a community sample of 4,662 6-year-old twin-pairs were sampled and 854 pairs were assessed in the second phase for normative repetitive routines using the Childhood Routines Inventory (CRI) and for OCSS by maternal-informant diagnostic interview. The OCSS phenotype was defined using standard diagnostic criteria for obsessive compulsive disorder, though regardless of impairment. Results: In the bivariate model, correlation between the CRI defined phenotype and the OCSS phenotype was estimated to be .40 (95% CI .27-.50), and this correlation was attributable wholly to additive genetic effects. The bivariate model also provided estimates of heritability of the two phenotypes separately: 55% (95% CI 80-89%) for the OCSS phenotype, with the remaining variance attributable mainly to non-shared environment, and 50% (95% CI 39-62%) for CRI assessed normative repetitive routines of childhood, with 36% of the remaining variance attributable to shared environment and 14% to non-shared. Conclusions: The moderate correlation between normative childhood repetitive routines and obsessive compulsive symptomatology, attributable to genetic factors, is consistent with the hypothesis that high levels of this trait in young children constitute a risk factor for the development of obsessive compulsive symptoms.