Abstract
Background: To assess whether the age-of-onset or the recurrence of parents' major depressive disorder (MDD), measured prospectively in a longitudinal birth cohort study, predicted offspring depression at age 15.
Methods: A two-generation study of New Zealanders, with prospective, longitudinal data in the parents' generation (n = 375) and cross-sectional data from their adolescent offspring (n = 612). Parent and offspring depression was measured with structured clinical interviews. Parent depression was measured at six time points from age 11 to 38 years. Adolescent offspring depression was measured at age 15.
Results Compared to adolescents whose parents were never depressed, those whose parents met criteria for MDD more than once and those whose parents first met criteria before adulthood had more symptoms of depression. The combination of early-onset and recurrent depression in parents made adolescents particularly vulnerable; their odds of meeting criteria for MDD were 4.21 times greater (95% CI = 1.57-11.26) than adolescents whose parents were never depressed. The strength of the intergenerational effect did not vary as a function of parent or offspring sex. The prevalence of adolescent depression was 2.5 times higher in the offspring than at age 15 in the parents' generation.
Conclusions: Recurrent depression in both fathers and mothers increases offspring risk for depression, particularly when it starts in childhood or adolescence, but a single lifetime episode does not. Health practitioners should be aware of age-of-onset and course of depression in both parents when assessing their children's risk for depression.