Relaxing effects of virtual environments on the autonomic nervous system indicated by heart rate variability: A systematic review

Recently, a number of virtual relaxation interventions (e.g., watching nature videos using virtual reality glasses) have been developed. Their effectiveness and factors influencing their success to induce physiological relaxation are unknown, however. This systematic review investigates first, whether virtual interventions can successfully induce changes in the autonomic nervous system associated with relaxation as measured by heart rate variability (HRV), and second, aims to determine whether specific intervention components exist which are necessary for their success. Online databases PubMed, Web of Science, and PsycInfo were included in the search. Out of 479 identified studies, 18 met the inclusion criteria, of which 17 found a significant physiological effect of a virtual relaxation intervention on HRV. Most used nature stimuli, either as pictures or videos, and assessed self-reported measurements in addition to HRV. Most studies also found an increase in HRV, with corresponding changes in various self-report measurements (e.g., decrease in anxiety). There was substantial heterogeneity between studies concerning the physiological outcome measures and details of the intervention. In summary, results from the included studies suggest that virtual relaxation interventions employing nature stimuli interventions are successful. Future studies should aim for a universal definition and operationalization of relaxation to allow easier comparison across different studies.