Investigating the Interaction of Sympathetic and Parasympathetic Nervous System Under Stress and Relaxation Using Guided Imagery

Abstract

The autonomic nervous system and the neuroendocrine system enable the body to switch between states of “fight/flight/freeze” and of “rest/digest” when coping with stressors or during recovery. The “rest/digest” or "relaxation" response, is crucial for regeneration processes, physiological homeostasis, and sustainment of physiological and psychological health. Here we asked whether a chronically stressed state is associated with an absence of an autonomic physiological relaxation response after acute stress. To do this, we investigated the effects of a relaxation intervention in acutely stressed individuals on neuroendocrine and autonomic markers trying to illustrate the interaction of sympathetic and parasympathetic nervous system. Healthy participants (N = 71) completed the socially evaluated cold pressor test before receiving a relaxation induction consisting of diaphragmatic breathing and guided imagery. Heart rate, heart rate variability (continuous electrocardiogram), salivary cortisol and salivary alpha amylase (saliva samples) were assessed as biological stress and relaxation markers. Mixed ANOVAs revealed a significant effect of the socially evaluated cold pressor test on cortisol levels and subjective stress. Additionally, a significant effect of the relaxation intervention on heart rate variability and heart rate was revealed (all p < .001). No significant differences in the ratio of the reactivity of the autonomic branches under stress and relaxation were found. The study confirms a successful induction of a neuroendocrine stress response via the socially evaluated cold pressor test and a successful induction of autonomic relaxation using the relaxation induction. Methodological limitations and indications for future studies are discussed.