title: Gene-environment interplay in depressive symptoms: moderation by age, sex, and physical illness.
abstract: BACKGROUND
  Numerous factors influence late-life depressive symptoms in adults, many not thoroughly characterized. We addressed whether genetic and environmental influences on depressive symptoms differed by age, sex, and physical illness.
  
  
  METHODS
  The analysis sample included 24 436 twins aged 40-90 years drawn from the Interplay of Genes and Environment across Multiple Studies (IGEMS) Consortium. Biometric analyses tested age, sex, and physical illness moderation of genetic and environmental variance in depressive symptoms.
  
  
  RESULTS
  Women reported greater depressive symptoms than men. After age 60, there was an accelerating increase in depressive symptom scores with age, but this did not appreciably affect genetic and environmental variances. Overlap in genetic influences between physical illness and depressive symptoms was greater in men than in women. Additionally, in men extent of overlap was greater with worse physical illness (the genetic correlation ranged from near 0.00 for the least physical illness to nearly 0.60 with physical illness 2 s.d. above the mean). For men and women, the same environmental factors that influenced depressive symptoms also influenced physical illness.
  
  
  CONCLUSIONS
  Findings suggested that genetic factors play a larger part in the association between depressive symptoms and physical illness for men than for women. For both sexes, across all ages, physical illness may similarly trigger social and health limitations that contribute to depressive symptoms.
authors.affiliation: Department of Neurology,University of Southern California,Los Angeles, CA,USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Petkus
authors.affiliation: Department of Psychology & Davis School of Gerontology,University of Southern California,Los Angeles, CAUSA.
authors.forename: C R
authors.initials: CR
authors.lastname: Beam
authors.affiliation: Department of Psychology,Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh,Edinburgh,UK.
authors.forename: W
authors.initials: W
authors.lastname: Johnson
authors.affiliation: Department of Public Health,University of Helsinki,Helsinki,Finland.
authors.forename: J
authors.initials: J
authors.lastname: Kaprio
authors.affiliation: Department of Public Health,University of Helsinki,Helsinki,Finland.
authors.forename: T
authors.initials: T
authors.lastname: Korhonen
authors.affiliation: Department of Psychology,University of Minnesota,Minneapolis, MN,USA.
authors.forename: M
authors.initials: M
authors.lastname: McGue
authors.affiliation: Department of Psychology,Penn State University,University Park,PA,USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Neiderhiser
authors.affiliation: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Stockholm,Sweden.
authors.forename: N L
authors.initials: NL
authors.lastname: Pedersen
authors.affiliation: Department of Psychology,University of California Riverside,Riverside, CA,USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Reynolds
authors.affiliation: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Stockholm,Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Gatz
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003863:Depression / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics*; D005260:Female; D059647:Gene-Environment Interaction; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology; D012737:Sex Factors
keywords: Aged; depressive symptoms; heritability; twin studies