Abstract
Depression and anxiety have frequently been observed to co-occur in the same individuals and the two disorders tend to aggregate in the same families. We investigated this overlap using structured diagnostic interview data collected from 3,372 pairs of male veteran twins in the Vietnam Era Twin Registry. Diagnoses of major depression (MD) and generalized anxiety disorder (GAD) were based on meeting DSM-III-R criteria, with the exception that for GAD we required one month of symptoms and did not exclude individuals whose anxiety symptoms occurred during depressive episodes. We carried out a bivariate analysis. The best fitting model included significant influences from additive genetic factors and the unique environment on MD and GAD; there was no significant influence from the family environment on either disorder. Heritabilities of 0.35 and 0.37 were observed for MD and GAD, respectively. The unique environment contributed 0.65 and 0.63 of the variance in MD and GAD, respectively. The genetic correlation between MD and GAD was 1.0 and the correlation between unique environmental influences on MD and GAD was 0.47. These results indicate that there is a complete overlap between the genetic factors influencing the risk of MD and GAD; there are no genes that contribute to one disorder without also contributing to the other. Genetic factors serve solely to produce overlap between the two disorders. However, some aspects of the unique environment promote cooccurrence of the two disorders, while other aspects of the unique environment impart risk for only MD or only GAD.
Original language | English |
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Pages (from-to) | 456 |
Number of pages | 1 |
Journal | American Journal of Medical Genetics - Neuropsychiatric Genetics |
Volume | 81 |
Issue number | 6 |
State | Published - Nov 6 1998 |