Objective: Epidemiological and clinical studies have established an association between major depression and cardiovascular disease. We utilized a twin design to test whether there are common genetic and environmental risk factors underlying depression symptoms, hypertension and heart disease.
Methods: Association studies were conducted with 6,903 male-male twins from the Vietnam Era Twin Registry who responded to both a 1990 health questionnaire and a 1992 telephone administration of a structured psychiatric interview. Data from 2,731 complete twin pairs were used to fit genetic models which determined the extent to which lifetime depression symptoms, heart disease and hypertension shared genetic and/or environmental factors.
Results: Heart disease was significantly associated with 1-4 symptoms and 5 or more symptoms of depression (odds ratio [OR] = 2.62; 95% confidence interval [CI]: 1.54-4.46 and OR = 4.02; 95% CI: 2.16-7.46). Hypertension was significantly associated with 1 to 4 symptoms and 5 or more symptoms of depression (OR = 1.29; 95% CI: 1.11-1.50 and OR = 1.49; 95% CI: 1.21-1.83). The genetic correlations were significant between depression symptoms and hypertension (r =.19), and between depression symptoms and heart disease (r =.42). Of the total variance in depression, 8% was common to hypertension and heart disease, 7% of the variance in hypertension was common with depression symptoms and heart disease, and 64% of the variance in heart disease was common with depression symptoms and hypertension.
Conclusions: Men who reported cardiovascular disease were significantly more likely to have depression symptoms. The lifetime co-occurrence of these phenotypes is partly explained by common genetic risk factors.