Physiological Responses to Virtual Reality-Based Stress Regulation and Relaxation Interventions: A Systematic Review.

Physiological markers are increasingly used to monitor individuals undergoing Virtual Reality (VR) stress interventions. However, several challenges arise when employing these markers to assess the impact of VR stress interventions. This systematic review synthesises and critically discusses the literature on VR stress interventions across contexts, study designs using physiological markers, marker usage, measurement setups, trends in interpreting data for stress recovery, and meanings assigned to marker changes. This review follows the PRISMA guidelines. EMBASE, IEEE Xplore, PsycINFO, PubMed, and Web of Science were searched until 12th March 2024. Studies were included if they used a head-mounted display (HMD) VR stress intervention and evaluated at least one physiological marker. The quality of studies was evaluated using the Evaluation Public Health Practice Project tool. Data were systematically extracted and summarised thematically and narratively. This review was registered with PROSPERO ID: CRD42024510162. Out of 11,479 articles identified, 69 studies were included: 59 conducted in the general population, four in mental healthcare, and six in the professional context. Study characteristics, experiment characteristics, and physiological outcomes were extracted. Most studies featured nature-based experiences, referenced Attention Restoration Theory (ART) and Stress Reduction Theory (SRT), and induced stress with mental arithmetic tasks or the Trier Social Stress Test (TSST). Many studies lacked theoretical grounding, had small sample sizes, conducted only a single VR session in a laboratory setting, and had low quality. Physiological markers and timepoints varied widely, with heart rate (HR), HRV (RMSSD, SDNN, LF, HF), and blood pressure being the most common. Fifty-six studies found that VR interventions reduced stress as measured by physiological markers. However, methodological inconsistencies limited their findings. Future research should prioritise ambulant measurements to improve real-world applicability and assess long-term effects. Additionally, standardising marker selection and measurement protocols is necessary to enhance validity and comparability, thereby strengthening evidence of VR stress interventions. TRIAL REGISTRATION: PROSPERO ID: CRD42024510162.