title: A 35-year longitudinal assessment of cognition and midlife depression symptoms: the Vietnam Era Twin Study of Aging.
abstract: OBJECTIVE
  To determine whether early adult cognitive ability is a risk factor for depressive symptoms in midlife and how genetic and environmental influences explain the association and to examine cross-sectional relationships between depressive symptoms and specific cognitive abilities at midlife.
  
  
  METHODS
  A 35-year longitudinal and cross-sectional twin study of cognitive aging.
  
  
  METHODS
  Large multicenter study in the United States.
  
  
  METHODS
  One thousand two hundred thirty-seven male twins aged 51 to 60 years.
  
  
  METHODS
  At the age of 20 years and midlife, participants completed the same version of a general cognitive ability test (Armed Forces Qualification Test [AFQT]). Midlife testing included an extensive neurocognitive protocol assessing processing speed, verbal memory, visual-spatial memory, working memory, executive function, and visual-spatial ability. Participants completed the Center for Epidemiologic Studies Depression Scale before cognitive testing and provided health and life style information during a medical history interview.
  
  
  RESULTS
  Lower age 20 AFQT scores predicted higher levels of depressive symptoms at age 55 years (r = -0.16,p <0.001). In bivariate twin modeling, 77% of the correlation between early cognitive ability and midlife depressive symptoms was due to shared genetic influences. Controlling for current age, age 20 AFQT, and nonindependence ofobservations, depressive symptoms were associated with worse midlife AFQT scores and poorer performance in all cognitive domains except verbal memory.
  
  
  CONCLUSIONS
  Results suggest that low cognitive ability is a risk factor for depressive symptoms; this association is partly due to shared genetic influences. Crosssectional analyses indicate that the association between depressive symptoms and performance is not linked to specific cognitive domains.
authors: Department of Psychiatry, University of California, San Diego, 92093, USA. cfranz@ucsd.edu
authors: Carol E
authors: CE
authors: Franz
authors: Michael J
authors: MJ
authors: Lyons
authors: Robert
authors: R
authors: O'Brien
authors: Matthew S
authors: MS
authors: Panizzon
authors: Kathleen
authors: K
authors: Kim
authors: Reshma
authors: R
authors: Bhat
authors: Michael D
authors: MD
authors: Grant
authors: Rosemary
authors: R
authors: Toomey
authors: Seth
authors: S
authors: Eisen
authors: Hong
authors: H
authors: Xian
authors: William S
authors: WS
authors: Kremen
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