Resting vagal activity in schizophrenia: meta-analysis of heart rate variability as a potential endophenotype.

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. AIMS: To quantify differences in HRV in individuals with schizophrenia compared with healthy controls.
METHOD: 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. © The Royal College of Psychiatrists 2016.