Parsing the genetic and nongenetic variance in children's depressive behavior.

Estimates of the genetic and environmental contributions to depressive behavior were derived using model-fitting analyses with data from a sample of 364 twin pairs, aged 4 to 12 years. Results suggested that genetic and nonshared environmental factors accounted for significant proportions of the variance in children's depressive symptomatology, but estimates differ for boys and girls. Further analyses indicated different genetic and environmental contributions for younger and older children. Analyses of a direct measure of shared and nonshared components of the environment identified specific aspects of children's environments which were associated with depressive behavior.