Cardiac autonomic functioning and post-traumatic stress: A preliminary study in youth at-risk for PTSD.

The identification of robust, psychophysiological markers of trauma-related distress is critical for developing comprehensive, trauma-informed, mental health assessments for youth. Thus, the present study examined the clinical utility of cardiac autonomic balance (CAB) and cardiac autonomic regulation (CAR), two composite indices of the sympathetic and parasympathetic nervous system. We hypothesized that CAB/CAR would more reliably index post-traumatic stress (PTS) responses compared to measuring the parasympathetic (i.e., respiratory sinus arrhythmia; RSA) and sympathetic (i.e., pre-ejection period; PEP) nervous systems in isolation. Our sample was comprised of 88 diverse, low-income youth (40.9% African-American and 36.4% White; 60.5% girls; Mage = 12.05 years; SDage = 1.57) who are at increased risk for adversity-exposure. RSA and PEP were measured during a 5-minute baseline period and 5-minute parent-child conflict discussion task. Adolescent-caregiver dyads completed a clinician-administered measure of the youth's lifetime trauma-exposure and current PTS. CAB represented the difference between RSA and PEP, while CAR was the summation of RSA and PEP. Analyses revealed that sympathetically-oriented CAB reactivity uniquely (a) indexed PTS, especially in the context of elevated trauma, and (b) distinguished between those with and without PTSD. Findings highlight the translational promise of using physiological markers that account for the balance between the parasympathetic and sympathetic nervous system.