title: Stability in symptoms of anxiety and depression as a function of genotype and environment: a longitudinal twin study from ages 3 to 63 years.
abstract: BACKGROUND
  The influence of genetic factors on major depressive disorder is lower than on other psychiatric disorders. Heritability estimates mainly derive from cross-sectional studies, and knowledge on the longitudinal aetiology of symptoms of anxiety and depression (SxAnxDep) across the lifespan is limited. We aimed to assess phenotypic, genetic and environmental stability in SxAnxDep between ages 3 and 63 years.
  
  
  METHODS
  We used a cohort-sequential design combining data from 49 524 twins followed from birth to age ⩾20 years, and from adolescence into adulthood. SxAnxDep were assessed repeatedly with a maximum of eight assessments over a 25-year period. Data were ordered in 30 age groups and analysed with longitudinal genetic models.
  
  
  RESULTS
  Over age, there was a significant increase during adolescence in mean scores with sex differences (women>men) emerging. Heritability was high in childhood and decreased to 30-40% during adulthood. This decrease in heritability was due to an increase in environmental variance. Phenotypic stability was moderate in children (correlations across ages ~0.5) and high in adolescents (r = 0.6), young adults (r = 0.7), and adults (r = 0.8). Longitudinal stability was mostly attributable to genetic factors. During childhood and adolescence there was also significant genetic innovation, which was absent in adults. Environmental effects contributed to short-term stability.
  
  
  CONCLUSIONS
  The substantial stability in SxAnxDep is mainly due to genetic effects. The importance of environmental effects increases with age and explains the relatively low heritability of depression in adults. The environmental effects are transient, but the contribution to stability increases with age.
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: M G
authors.initials: MG
authors.lastname: Nivard
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: C V
authors.initials: CV
authors.lastname: Dolan
authors.affiliation: Departments of Psychiatry and Human and Molecular Genetics,Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: K J
authors.initials: KJ
authors.lastname: Kan
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Willemsen
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: C E M
authors.initials: CE
authors.lastname: van Beijsterveldt
authors.affiliation: Department of Child and Adolescent Psychiatry,Amsterdam Medical Center,Amsterdam,The Netherlands.
authors.forename: R J L
authors.initials: RJ
authors.lastname: Lindauer
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: J H D A
authors.initials: JH
authors.lastname: van Beek
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: L M
authors.initials: LM
authors.lastname: Geels
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Bartels
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: C M
authors.initials: CM
authors.lastname: Middeldorp
authors.affiliation: Department of Biological Psychology,VU University Amsterdam,The Netherlands.
authors.forename: D I
authors.initials: DI
authors.lastname: Boomsma
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000235:genetics* / Q000523:psychology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003863:Depression / Q000235:genetics* / Q000523:psychology; D018450:Disease Progression; D004777:Environment; D005260:Female; D059647:Gene-Environment Interaction; D005838:Genotype; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012931:Social Environment; D014429:Twins, Dizygotic / Q000235:genetics* / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics* / Q000523:psychology; D055815:Young Adult
keywords: longitudinal genetic analysis