Genetic and environmental influences on obsessional traits and symptoms

A biometrical genetic analysis was carried out on the response of 419 pairs of twins to the 42-item version of Leyton Obsessional Inventory. Just under half the variation in both the Obsessional Trait and Symptom Scales was due to heredity. Multivariate analysis revealed a genetic effect on the development of obsessional personality and also the transmission of a general tendency predisposing to neurotic breakdown. Although the influence of heredity was outweighed by that of the environment, the latter effect showed an absence of general factors and, in particular, of any noticeable effect from the common home environment.