Genetic and environmental influences on the temporal association between earlier anxiety and later depression in girls

Background: The purpose of the present study was to investigate the role of genetic and environmental factors in the association between depressive symptoms and symptoms of overanxious disorder, simple phobias, and separation anxiety in 8–13-year-old and 14–17-year-old girls. Methods: Multivariate genetic models were fitted to child-reported longitudinal symptom data gathered from clinical interview on 415 monozygotic and 194 dizygotic female twin pairs from the Virginia Twin Study of Adolescent Behavioral Development. Results: Model-fitting results suggest there are distinct etiologic patterns underlying the association between depression and the different anxiety syndromes during the course of development: 1) specific genetic influences on depression after age 14 reflect liability to symptoms of earlier overanxious disorder (OAD) and simple phobias; 2) aspects of the shared environment that influence symptoms of depression before age 14 contribute to symptoms of separation anxiety and simple phobias; 3) later in adolescence shared environmental influences depression in 14+ girls also affects liability to symptoms of concurrent OAD and persistent separation anxiety. Conclusions: These results suggest that depression before and after age 14 may be etiologically distinct syndromes. Earlier symptoms of OAD and (to a lesser extent) phobic symptoms reflect the same genetic risk, and separation anxiety symptoms both before and after age 14 reflect the same environmental risk that influences liability to depressive symptoms expressed in middle to late adolescence.