Abstract
Changes in autonomic nervous system (ANS) function have been observed in a variety of psychological disorders, including posttraumatic stress disorder (PTSD). Analysis of heart rate variability (HRV) provides insight into the functioning of the ANS. Previous research on PTSD found lower HRV in PTSD patients compared to controls, indicating altered sympathetic and parasympathetic activity, but findings are inconsistent. The purpose of this meta-analysis was to examine differences in HRV indices between individuals with PTSD and healthy controls at baseline and during stress. The included primary studies present an aggregate of studies analyzing different HRV indices. Examined HRV indices were standard deviation of the normalized NN-intervals (SDNN), root mean square of successive differences (RMSSD), low-frequency (LF) and high-frequency (HF) spectral components, LF/HF ratio, and heart rate (HR). Moderating effects of study design, HRV and PTSD assessment, and sample characteristics were examined via subgroup-analyses and meta-regressions. Random-effects meta-analyses for HRV parameters at rest revealed significant group differences for RMSSD and HF-HRV, suggesting lower parasympathetic activity in PTSD. The aggregated effect size for SDNN was medium, suggesting diminished total variability in PTSD. A small effect was found for LF-HRV. A higher LF/HF ratio was found in the PTSD sample as compared to controls. Individuals with PTSD showed significantly higher HR. During stress, individuals with PTSD showed higher HR and lower HF-HRV, both indicated by small effect sizes. Findings suggest that PTSD is associated with ANS dysfunction.
Highlights
Exposure to traumatic life events can have severe effects on the functioning of physiological systems, including the autonomic nervous system (ANS) (Orr & Roth, 2000)
I2 refers to the amount of variation between studies that is based on true variation in effect size and is interpreted according to benchmarks set by Higgins and Thompsons (20022002): ≈25% low, ≈50% moderate and ≈75% high level of heterogeneity
Exclusion of the outliers lead to a decrease in the effect size [Hedges’ g = −0.50, p < 0.001]
Summary
Exposure to traumatic life events can have severe effects on the functioning of physiological systems, including the autonomic nervous system (ANS) (Orr & Roth, 2000). A meta-analysis by Pole (2007) revealed that resting heart rate is increased in patients with PTSD as compared to healthy controls. Alterations in arousal may change cardiovascular stress activity and reactivity This can lead to either increased or blunted responsiveness of individuals with PTSD to challenging and stressful tasks (Cohen et al, 2000; Dennis et al, 2016; Jovanovic, Norrholm, Sakoman, Esterajher, & Kozarić-Kovačić, 2009). HRV parameters were lower in PTSD patients compared to controls, indicated by medium to large effect sizes. The aim of the current meta-analysis was to examine differences in HRV parameters between individuals with PTSD and controls, both at rest and during stress tasks.
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