This study seeks to clarify the etiologic importance and temporal stability of the genetic and environmental risk factors for 1-year prevalence of major depression (1YP-MD) in women.
One-year prevalence of major depression was personally assessed, using DSM-III-R criteria, at two time points a minimum of 1 year apart.
Both members of 938 adult femalefemale twin pairs ascertained from the population-based Virginia Twin Registry.
The correlation in liability to 1YP-MD was much greater in monozygotic (MZ) than in dizygotic (DZ) twins at time 1 alone, time 2 alone, or at either time 1 or time 2. Model fitting suggested that the liability to 1YP-MD was due to additive genes and individual specific envi- ronment with a heritability of 41% to 46% and was not biased by violations of the equal environment assumption. Jointly analyzing both times of assessment using a longitudinal twin model suggested that, over a 1-year period, genetic effects on the liability to 1YP-MD were entirely stable, while environmental effects were entirely occasion specific.
These results suggest that (1) genetic factors play a moderate etiologic role in the 1YP-MD, (2) the temporal stability of the liability to major depression in adult women is largely or entirely genetic in origin, and (3) environmental factors play a significant role in the etiology of major depression, but their effects are generally transitory and do not result in enduring changes in the liability to illness.
Kendler KS, Neale MC, Kessler RC, Heath AC, Eaves LJ. A Longitudinal Twin Study of 1-Year Prevalence of Major Depression in Women. Arch Gen Psychiatry. 1993;50(11):843-852. doi:10.1001/archpsyc.1993.01820230009001