A comparative evaluation of resting state proxies of sympathetic and parasympathetic nervous system activity in adolescent major depression

: Major depressive disorder (MDD) is associated with autonomic nervous system (ANS) dysfunction, characterized by decreased parasympathetic (PNS) and increased sympathetic (SNS) activity. Although findings on reduced PNS activity in adult MDD have been replicated in adolescents, comprehensive studies assessing PNS and SNS proxies in underage patients with MDD are scarce. Proxies of resting PNS (heart rate variability (HRV) and SNS activity (skin conductance response [SCR] and salivary alpha amylase [sAA], as well as mixed activity (heart rate [HR]) were collected in adolescents with MDD (n = 29) and non-depressed controls (n = 29). Primary analyses addressed differences between groups and correlations with depression severity. Patients with MDD showed significantly decreased HRV (g = - 0.87; 95% CI [- 1.39; - 0.35]) and increased HR (g = 0.66; 95% CI [0.14; 1.18]). Proxies of pure SNS activity showed no significant differences between groups. HR (positive) and HRV (negative) were significantly correlated with self- and clinician-rated depression severity. Alterations of ANS activity are evident in adolescent MDD, but characterized by decreased PNS activity only. We found no evidence for altered SNS activity. Findings suggest that ANS dysfunction early in the course of MDD might be predominantly driven by decreased PNS activity.