Adverse Childhood Experiences Modify the Effect of Nature on Stress Recovery Among Males: A Between-Subjects Experiment in Virtual Reality

Abstract

Background: Studies have demonstrated that exposure to nature decreases acute stress responses, and that adverse childhood experiences (ACEs) are linked to physiological hyperreactivity to acute psychosocial stressors. Nature exposure may therefore have potential to act as a protective factor against the heightened stress responses that are associated with high ACEs. We investigated whether ACEs, and other measures of stress vulnerability, modified the effects of virtual nature exposure on physiological responses to an acute psychosocial stressor, and subsequent recovery in contrasting environmental conditions, among 95 healthy adult males.Methods: Baseline assessments included the ACE questionnaire, the Miller-Smith Lifestyle Assessment Inventory (stress vulnerability) and immunological hyperactivity; measured via immune cell interleukin-6 production after lipopolysaccharides (LPS) exposure. We then conducted an experiment in which participants experienced an acute stressor (Trier Social Stress Test), followed by randomly assigned exposure to one of three virtual environments (natural park, natural desert, or control [office]) for 10-min, followed by two 20-min recovery periods. Physiological stress indicators, including systolic and diastolic blood pressure (SBP & DBP), pulse, mean arterial pressure (MAP) and salivary cortisol, were measured repeatedly throughout the experimental sessions.Results: We found that high-ACE, stress-vulnerable and LPS-hyperactive participants exhibited physiological hyperreactivity to the stressor. During the recovery periods, high-ACE and LPS-hyperactive participants in the natural park condition experienced greater drops in blood pressure vs. low-ACE and non-LPS-hyperactive participants. Additionally, high-ACE participants in the desert condition showed greater decreases in DBP vs. low-ACE participants.Conclusions: High-ACE participants responded differently to both the acute stressor and the virtual natural environments than low-ACE participants. This indicates that assessments of ACEs may be a critical consideration when examining the ways in which the stress-buffering effects of nature exposure may vary across individuals and subpopulations, and opens up a new set of questions about why this may be the case.