title: A longitudinal twin study of 1-year prevalence of major depression in women.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  One-year prevalence of major depression was personally assessed, using DSM-III-R criteria, at two time points a minimum of 1 year apart.
  
  
  METHODS
  Both members of 938 adult female-female twin pairs ascertained from the population-based Virginia Twin Registry.
  
  
  RESULTS
  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 environment 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Psychiatry, Medical College of Virginia/Virginia Commonwealth University, Richmond.
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
authors.forename: M C
authors.initials: MC
authors.lastname: Neale
authors.forename: R C
authors.initials: RC
authors.lastname: Kessler
authors.forename: A C
authors.initials: AC
authors.lastname: Heath
authors.forename: L J
authors.initials: LJ
authors.lastname: Eaves
mesh_terms: D000328:Adult; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D004200:Diseases in Twins / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008957:Models, Genetic; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014768:Virginia / Q000453:epidemiology