title: Depressive symptoms and heart rate variability: evidence for a shared genetic substrate in a study of twins.
abstract: OBJECTIVE
  To clarify the relationship between depression and heart rate variability (HRV) in a sample of twins. Reduced HRV, a measure of autonomic dysfunction, has been linked to depression but many studies have inadequately controlled for familial and environmental factors. Furthermore, little is known about whether depression and HRV share common genetic pathways.
  
  
  METHODS
  We performed power spectral analysis on 24-hour ambulatory electrocardiograms in 288 middle-aged male twins. Log-normalized ultra low, very low, low, high frequency, and total power were calculated. A lifetime history of major depressive disorder (MDD) was determined, using the Structured Clinical Interview for Psychiatry Disorders, and current depressive symptoms were measured with the Beck Depression Inventory. Mixed-effect regression models were used to account for intrapair variability and estimate within-pair effects at the same time controlling for potential confounders.
  
  
  RESULTS
  Both current depressive symptoms and a history of MDD were significantly associated with lower HRV. There was a graded effect, and power in each frequency band was 29% to 36% lower in the lowest band compared with the highest BDI category. All HRV measures except high frequency remained significantly associated with current depressive symptoms in multivariable analysis, but not with lifetime history of MDD. When analyses were stratified by zygosity, a significant within-pair association between BDI score and HRV was found in the dizygotic but not in the monozygotic twins, suggesting a genetic influence on the association.
  
  
  CONCLUSIONS
  A shared, genetically influenced biological pathway underlies the association between depression and lower HRV. These two phenotypes may be the expression of a generalized neurobiological perturbation.
authors.affiliation: Division of Cardiology, Department of Medicine, Emory University School of Medicine, 1256 Briarcliff Road NE, Suite-1 North, Atlanta, GA 30306, USA. viola.vaccarino@emory.edu
authors.forename: Viola
authors.initials: V
authors.lastname: Vaccarino
authors.forename: Rachel
authors.initials: R
authors.lastname: Lampert
authors.forename: J Douglas
authors.initials: JD
authors.lastname: Bremner
authors.forename: Forrester
authors.initials: F
authors.lastname: Lee
authors.forename: Shaoyong
authors.initials: S
authors.lastname: Su
authors.forename: Carisa
authors.initials: C
authors.lastname: Maisano
authors.forename: Nancy V
authors.initials: NV
authors.lastname: Murrah
authors.forename: Linda
authors.initials: L
authors.lastname: Jones
authors.forename: Farhan
authors.initials: F
authors.lastname: Jawed
authors.forename: Nadeem
authors.initials: N
authors.lastname: Afzal
authors.forename: Ali
authors.initials: A
authors.lastname: Ashraf
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology*; D003327:Coronary Disease / Q000235:genetics / Q000523:psychology; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000175:diagnosis* / Q000235:genetics / Q000523:psychology*; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D004200:Diseases in Twins / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D015716:Electrocardiography, Ambulatory / Q000379:methods; D006339:Heart Rate; D006801:Humans; D007406:Interview, Psychological / Q000379:methods; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D014728:Veterans / Q000523:psychology