The influence of genetic factors and life stress on depression among adolescent girls

Background: The possible causes of greater depression among adolescent girl s were investigated by examining variation in the influence of genetic and environmental risk factors among 182 prepubertal female, 237 prepubertal ma le, 314 pubertal female, and 171 pubertal male twin pairs from the Virginia Twin Study of adolescent Behavioral Development. Objectives: To compare the trajectory of depressive symptoms among boys and girls from childhood to adolescence; to analyze the role of genetic, share d, and unique environmental factors in depression among prepubertal and pub ertal male and female twins; and to investigate a possible link between lia bility to depression and one salient index of the child's environment: past -year life events. Methods: Child-reported depression was assessed using the Child and Adolesc ent Psychiatric Interview and ratings of past-year life events and pubertal status obtained by maternal questionnaire and interview, respectively. Results: The impact of life events on depression was particularly evident i n the adolescent girls. The results from model fitting indicate increased h eritability for depression in this group, and its long-term consistency was mediated primarily by latent genetic factors. Model fitting also showed th at at least part of the liability to depression and to life events can be l inked to a common set of genes in the adolescent girls, and there is a nota ble developmental increase in the genetic variance for life events. Conclusions: The greater heritability for depression in pubertal girls, its genetic mediation over time, and the increase in genetic variance for life events may be one possible explanation for the emergence of increased depr ession among pubertal girls and its persistence through adolescence.