Sex differences in genetic and environmental contributions to depression symptoms in South Korean adolescent and young adult twins

It has been reported that prevalence estimates, symptom presentation, and sociocultural risk and protective factors for depression differ between Caucasian and East Asian populations. But, nonetheless, as the vast majority of twin studies of depression symptoms have been carried out using Caucasians, genetic and environmental influences on depression symptoms in East Asians remain poorly understood. In the present study, the Center for Epidemiologic Studies - Depression Scale (CES-D) was administered to 490 pairs of South Korean adolescent and young adult twins (ages: 13-23 years) by telephone interview. In males, monozygotic (MZ) and dizygotic (DZ) twin correlations were similar (.44 vs. .41), suggesting the importance of shared environmental factors in depression symptoms. In females, however, MZ twin correlation was much greater than DZ twin correlation (.40 vs. .23), indicating the importance of genetic influences. The total phenotypic variance for the CES-D was greater in females than in males. Variance components model confirmed sex differences in the magnitude of genetic and environmental influences on depression symptoms: Additive genetic, shared environmental, and individual specific environmental effects in the full model were, respectively, 12% (95% CI: 0-54%), 32% (95% CI: 0-53%), and 56% (95% CI: 44-70%) in males, and 41% (95% CI: 0-52%), 0% (95% CI: 0-36%), and 59% (95% CI: 48-72%) in females. Similar results were observed when 'culturally biased' items of the CES-D were separately analyzed. These variance components estimates for depression symptoms in East Asians overlap those observed in Caucasians.