This study evaluates the feasibility, acceptability and clinical impact of a virtual reality (VR)- based nature intervention in an acute psychiatric inpatient unit. Participants are randomly assigned to recieve VR nature sessions (using Nature Treks VR on Meta Quest 3) in addition to standard care, or standard care alone. The primary outcome is change in percieved stress (PSS-19) from admission to discharge. The study uses a mixed-methods design combining randomized controlled trial with a qualitative phase.

THE GREEN ROOM is a sequential, explanatory mixed-methods study comprising two phases. Phase 1 is a qualitative study (n=40; patients and healthcare professionals) using the Non-adoption, Abandonment, Scale-up, Spread, and Sustainability (NASSS) framework to identify barriers and facilitators to VR implementation in an acute psychiatric ward, and to co-create the final VR intervention content with patients and staff. Phase 2 is the randomised controlled trial described in this record.

Phase 2 participants are randomised 1:1 to receive VR-based nature exposure sessions (Nature Treks VR, Meta Quest 3) in addition to treatment as usual, or treatment as usual alone. Randomisation is stratified by legal admission status (voluntary vs. involuntary) using two separate pre-generated sequential allocation lists (n=60 per stratum). Allocation concealment is maintained through sequential, pre-fixed assignment managed by the research assistant; the Principal Investigator remains blinded to individual allocations during data collection, and the statistical analyst remains blinded until the analysis plan is finalised and locked.

Intervention-group participants are offered VR sessions of 10\u201315 minutes approximately every other day throughout hospitalisation, on a strictly voluntary basis. Participants may freely choose and switch between all nature environments available within the Nature Treks VR application. During the first VR session, a consecutive sub-sample of intervention participants (estimated n\u224850) additionally undergo physiological monitoring (heart rate and heart rate variability) using a consumer-grade wearable device (Fitbit).

The primary analysis will use a mixed-design ANOVA (or ANCOVA with baseline score as covariate) to evaluate change in PSS-10 from admission to discharge, following an intention-to-treat approach. Missing data will be handled under a Missing-At-Random assumption within the mixed-effects model framework, with complete-case analysis as a sensitivity check. Two exploratory subgroup analyses are pre-specified: by legal admission status and by primary diagnostic category.

Inclusion Criteria:

Adults aged 18 to 65 years. Admitted to the Acute Psychiatry Ward (regardless of voluntary or involuntary legal status).

Sufficient cognitive and clinical stability to provide informed consent and engage with the VR equipment, as determined by the clinical team.

Ability to communicate effectively in Spanish.

Exclusion Criteria:

History of photosensitive epilepsy or severe seizure disorders. Presence of active facial injuries, infections, or skin conditions that prevent the hygienic use of the VR headset.

Pre-existing severe vertigo, balance disorders, or high susceptibility to motion sickness.

Acute clinical state involving high risk of agitation or behavioral dysregulation that could compromise participant or equipment safety.

Severe visual or hearing impairments that cannot be corrected and would hinder the VR experience.

Patients who have previously participated in the study during a prior admission are not eligible for re-enrolment.