Post-traumatic stress disorder (PTSD) symptom clusters associated with an indicator of heart rate variability: The ADVANCE cohort study

Background: Heart rate variability (HRV) is governed by sympathetic and parasympathetic regulatory systems. Post-Traumatic Stress Disorder (PTSD) may influence these systems and consequently affect cardiovascular functioning. Methods: The sample consisted of 860 UK male military personnel approximately half of whom had sustained physical combat injuries in Afghanistan. HRV was measured via Root-Mean Square of Successive Differences (RMSSD) in normal heart beats and PTSD using a self-report questionnaire (Posttraumatic Checklist-Civilian version (PCL)). Associations between probable PTSD status (PCL score >= 50) and symptom clusters (avoidance behaviours, emotional numbing, hyperarousal and intrusive thoughts) with HRV were examined. Bootstrap inclusion frequencies and model averaging were employed prior to regression modelling to identify the most important symptom clusters associated with RMSSD. Results: Probable PTSD status was not associated with log RMSSD [- 11.6 % (95 % Confidence Interval (CI)-22.2 %, 4.1 %). Increases in severity of emotional numbing were associated with reductions in RMSSD, with a- 1.1 % (95%CI-2.1 %,-0.2 %) decrease in the geometric mean of RMSSD per point increase on the emotional numbing subscale. Limitations: High levels of comorbidity with depression/anxiety; possible endogeneity/bidirectionality due to PCL including both psychological and physiological symptoms. Conclusions: Emotional numbing, the symptom cluster including symptoms such as anhedonia, cognitive dysregulation and feeling distant from other people, was associated with lower HRV whilst overall PTSD status was not. These results lend support to the hypothesis that different PTSD symptom clusters may have unique effects on the cardiovascular system, and that particular symptom clusters of PTSD or combinations thereof may be associated with distinctive cardiovascular profiles.