A multi-level meta-analysis of vagally-mediated heart rate variability and post-traumatic stress disorder.

Posttraumatic stress disorder (PTSD) is frequently associated with autonomic nervous system (ANS) dysregulation, as evidenced by diminished vagally mediated heart rate variability (vmHRV). To date, no meta-analysis has systematically compared 5-minute and 24-hour vmHRV recordings in PTSD, limiting our understanding of how recording duration influences findings. This study examined differences in vmHRV between individuals with PTSD and controls using both 5-minute and 24-hour recordings. The meta-analysis synthesised data from 24 studies involving 2537 participants and 34 effect sizes. A novel analytical approach was used and involved traditional multi-level meta-analysis, robust variance estimation, and separate analyses across vmHRV indices and recording durations to isolate independent effects. Whilst vmHRV was consistently reduced in individuals with PTSD, the magnitude of this effect was greater in studies utilising 5-minute recordings than those using 24-hour recordings. Therefore, the results indicate that methodological differences in HRV assessment, particularly recording duration, significantly influence the observed magnitude of vmHRV reductions in PTSD. The robust analytical strategy enhances the reliability of vmHRV as a biomarker of ANS dysregulation in PTSD. The findings highlight the need for standardised vmHRV protocols in PTSD research.