title: Depression, comorbid anxiety disorders, and heart rate variability in physically healthy, unmedicated patients: implications for cardiovascular risk.
abstract: BACKGROUND
  There is evidence that heart rate variability (HRV) is reduced in major depressive disorder (MDD), although there is debate about whether this effect is caused by medication or the disorder per se. MDD is associated with a two to fourfold increase in the risk of cardiac mortality, and HRV is a robust predictor of cardiac mortality; determining a direct link between HRV and not only MDD, but common comorbid anxiety disorders, will point to psychiatric indicators for cardiovascular risk reduction.
  
  
  OBJECTIVE
  To determine in physically healthy, unmedicated patients whether (1) HRV is reduced in MDD relative to controls, and (2) HRV reductions are driven by MDD alone, comorbid generalized anxiety disorder (GAD, characterized by anxious anticipation), or comorbid panic and posttraumatic stress disorders (PD/PTSD, characterized by anxious arousal).
  
  
  METHODS
  A case-control study in 2006 and 2007 on 73 MDD patients, including 24 without anxiety comorbidity, 24 with GAD, and 14 with PD/PTSD. Seventy-three MDD and 94 healthy age- and sex-matched control participants were recruited from the general community. Participants had no history of drug addiction, alcoholism, brain injury, loss of consciousness, stroke, neurological disorder, or serious medical conditions. There were no significant differences between the four groups in age, gender, BMI, or alcohol use.
  
  
  METHODS
  HRV was calculated from electrocardiography under a standardized short-term resting state condition.
  
  
  RESULTS
  HRV was reduced in MDD relative to controls, an effect associated with a medium effect size. MDD participants with comorbid generalized anxiety disorder displayed the greatest reductions in HRV relative to controls, an effect associated with a large effect size.
  
  
  CONCLUSIONS
  Unmedicated, physically healthy MDD patients with and without comorbid anxiety had reduced HRV. Those with comorbid GAD showed the greatest reductions. Implications for cardiovascular risk reduction strategies in otherwise healthy patients with psychiatric illness are discussed.
authors.affiliation: School of Psychology, University of Sydney, Sydney, New South Wales, Australia. andrew.kemp@sydney.edu.au
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Kemp
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Quintana
authors.forename: Kim L
authors.initials: KL
authors.lastname: Felmingham
authors.forename: Slade
authors.initials: S
authors.lastname: Matthews
authors.forename: Herbert F
authors.initials: HF
authors.lastname: Jelinek
mesh_terms: D000328:Adult; D001008:Anxiety Disorders / Q000150:complications* / Q000523:psychology; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000209:etiology* / Q000523:psychology; D016022:Case-Control Studies; D015897:Comorbidity; D003865:Major Depressive Disorder / Q000150:complications* / Q000523:psychology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male