title: Resting vagal activity in schizophrenia: meta-analysis of heart rate variability as a potential endophenotype.
abstract: BACKGROUND
  Cardiac vagal tone, indexed by heart rate variability (HRV), is a proxy for the functional integrity of feedback mechanisms integrating central and peripheral physiology.
  
  
  OBJECTIVE
  To quantify differences in HRV in individuals with schizophrenia compared with healthy controls.
  
  
  METHODS
  Databases were systematically searched for studies eligible for inclusion. Random effect meta-analyses of standardised mean differences were calculated for vagal activity indicated by high-frequency HRV and the root mean square of successive R-R interval differences (RMSSD).
  
  
  RESULTS
  Thirty-four studies were included. Significant main effects were found for high-frequency HRV (P = 0.0008; Hedges' g = -0.98, 95% CI -1.56 to -0.41, k = 29) and RMSSD (P<0.0001; g = -0.91, 95% CI -1.19 to -0.62, k = 24), indicating lower vagal activity in individuals with schizophrenia than in healthy controls. Considerable heterogeneity was evident but effects were robust in subsequent sensitivity analyses.
  
  
  CONCLUSIONS
  Given the association between low HRV, threat processing, emotion regulation and executive functioning, reduced vagal tone may be an endophenotype for the development of psychotic symptoms.
authors.affiliation: Annika Clamor, MSc, Tania M. Lincoln, Dr. rer. nat., University of Hamburg, Department of Clinical Psychology and Psychotherapy, Hamburg, Germany; Julian F. Thayer, PhD, The Ohio State University, Department of Psychology, Columbus, Ohio, USA; Julian Koenig, Dr. sc. hum., University of Heidelberg, Department of Child and Adolescent Psychiatry, Section for Translational Psychobiology in Child and Adolescent Psychiatry, Heidelberg, Germany annika.clamor@uni-hamburg.de.
authors.forename: Annika
authors.initials: A
authors.lastname: Clamor
authors.affiliation: Annika Clamor, MSc, Tania M. Lincoln, Dr. rer. nat., University of Hamburg, Department of Clinical Psychology and Psychotherapy, Hamburg, Germany; Julian F. Thayer, PhD, The Ohio State University, Department of Psychology, Columbus, Ohio, USA; Julian Koenig, Dr. sc. hum., University of Heidelberg, Department of Child and Adolescent Psychiatry, Section for Translational Psychobiology in Child and Adolescent Psychiatry, Heidelberg, Germany.
authors.forename: Tania M
authors.initials: TM
authors.lastname: Lincoln
authors.affiliation: Annika Clamor, MSc, Tania M. Lincoln, Dr. rer. nat., University of Hamburg, Department of Clinical Psychology and Psychotherapy, Hamburg, Germany; Julian F. Thayer, PhD, The Ohio State University, Department of Psychology, Columbus, Ohio, USA; Julian Koenig, Dr. sc. hum., University of Heidelberg, Department of Child and Adolescent Psychiatry, Section for Translational Psychobiology in Child and Adolescent Psychiatry, Heidelberg, Germany.
authors.forename: Julian F
authors.initials: JF
authors.lastname: Thayer
authors.affiliation: Annika Clamor, MSc, Tania M. Lincoln, Dr. rer. nat., University of Hamburg, Department of Clinical Psychology and Psychotherapy, Hamburg, Germany; Julian F. Thayer, PhD, The Ohio State University, Department of Psychology, Columbus, Ohio, USA; Julian Koenig, Dr. sc. hum., University of Heidelberg, Department of Child and Adolescent Psychiatry, Section for Translational Psychobiology in Child and Adolescent Psychiatry, Heidelberg, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Koenig
mesh_terms: D001921:Brain / Q000503:physiopathology*; D004644:Emotions; D058068:Endophenotypes; D056344:Executive Function; D006339:Heart Rate; D006801:Humans; D012559:Schizophrenia / Q000503:physiopathology*; D014630:Vagus Nerve / Q000503:physiopathology*