The association between depressive mood and ischemic heart disease: a twin study

Objective: Individuals with mood disorders have increased risk of cardiovascular disease. The aims of this study were to evaluate if the risk of cardiovascular disease in individuals with mood disorder could be explained by shared genetic and early environmental factors. Methods: We included 6714 Danish middle and old aged twins from two large population-based studies. Cox proportional hazards regression was used to perform individual-level and intra-pair analyses of the association between self-reported depression symptomatology scores and register-based diagnoses of ischemic heart disease. Results: Higher depression symptomatology scores (both total, affective, and somatic) were associated with higher incidence of ischemic heart disease after multivariable adjustment in individual-level analyses. In intra-pair analyses, this association was similar but with slightly larger confidence intervals. There was no interaction with gender and no major differences between mono- or dizygotic twins. Within twin pairs, the twin scoring highest on depressive symptoms developed ischemic heart disease more often or earlier than the lower scoring twin. A sensitivity analysis including a 2-year time lag of depression symptomatology to limit the risk of reverse causality showed similar results. Conclusion: Genetic factors and early life environment do not seem to explain the association between depressive mood and ischemic heart disease.