Genetic and environmental effects on the development of depressive symptoms from adolescence to adulthood in a nationally representative sample

Abstract

BackgroundPrevious research has shown substantial heritability for depressive symptoms, yet, there are few genetically-informed studies which focused on developmental changes. The current study sought to model prototypical developmental trajectories of depressive symptoms from adolescence to adulthood and to elucidate genetic and environmental contributions to these changes. MethodsThe Add Health data set, a nationally representative sample of adolescents, was used. For the genetically-informed analyses, a subsample of N = 531 same-sex monozygotic and dizygotic male and female twin pairs was selected. Longitudinal development was modeled separately for two waves in early adolescence and for four waves from middle adolescence to young adulthood using a latent growth model (LGM). Both models were extended to twin models to estimate the effects of heritability and the environment. ResultsThe rates of depressive symptoms peaked in mid-adolescence and then sharply declined as individuals moved from adolescence to young adulthood, leveling off in the twenties. The effects of the shared environment were substantial among early adolescents, but negligible for middle-to-late adolescents. An opposite pattern was found for heritability. The largest proportion of developmental changes was driven by nonshared environmental effects. LimitationsThe study only used same-sex twins as there exist mixed findings regarding the possibility of qualitative or quantitative genetic effects. ConclusionsThe salience of unique experiences and, to a lesser extent, heritable factors in affecting developmental changes in depressive symptoms underscore the need for targeting environments that place individuals with genetic predisposition at double the risk for the development of depression.