The Nature of Covariation between Separation Anxiety Symptoms and Obsessive Compulsive Symptoms in Developmental Age

In spite of the high rates of comorbidity between Obsessive Compulsive Symptoms and Separation Anxiety Symptoms, no previous study, to our knowledge, has explored the nature of the covariation between these two phenotypes in developmental age. In three-hundred-ninety-eight twin pairs belonging to the population-based Italian Twin Registry, we investigated by behavioral genetics approach whether the phenotypic correlation between Obsessive Compulsive Symptoms and Separation Anxiety Symptoms could better be accounted for by direct, causal effect, or by the presence of latent causal factors, acting simultaneously as elements of risk for these two phenotypes. Significant correlation was found between Obsessive Compulsive Symptoms and Separation Anxiety Symptoms. Results from Causal Analysis indicated that shared factors of liability, rather than direct causation, better explained the phenotypic correlation between these phenotypes. Bivariate analyses showed shared genetic factors that simultaneously influence Obsessive Compulsive Symptoms and Separation Anxiety Symptoms as the best explanation for the phenotypic covariation. The same gene pools that influence high scores of Separation Anxiety symptoms cause also high level of Obsessive Compulsive symptoms. Although individual-specific experiences appear to play a significant role in accounting for the variance of all phenotypes under study, their influence on covariation was found to be negligible.