Stress refers to the physiological, psychological, and behavioral responses to demands or perceived threats that challenge individuals’ resources to manage them [1,2]. This study focuses on the psychological stress response, operationalized as the level of perceived distress and corresponding affective states (eg, feeling anxious, nervous, or down, and less calm, cheerful, or content).

Stress responses are often adaptive but also can increase vulnerability to disease. In psychiatry, stress is a transdiagnostic factor that has been related to both onset, course, and recurrence of mood, anxiety, and psychotic disorders [3,4]. Stress-reducing interventions such as breathing exercises, mental imagery, progressive muscle relaxation, and mindfulness are commonly applied in routine mental health care. These interventions are effective for reducing anxiety, stress, and sleeping problems [5,6], have some effects on level of depressive symptoms [7,8], and have hardly been investigated in patients with psychotic disorders [9]. Another intervention known to reduce stress is exposure to natural environments. Consistent associations have been reported between stress level (physiological and subjective) and time spent in green and blue spaces [10-12]. Negative impact of stress on health may be alleviated by presence of green space [13].

Although stress-reducing interventions may be effective, they are challenging for people with mental health problems. They require initiative, concentration, sustained attention, and energy, which are reduced in many psychiatric disorders, especially in association with exposure to stress [14]. There is a need for easy-to-use stress-reducing interventions that require less effort. Virtual reality (VR) technology offers opportunities to overcome the aforementioned challenges. A combination of visual and auditory stimuli in VR can be used to create an immersive experience that may reduce perceived distress and negative affect without much effort and induce relaxation and positive affect. VR treatments have been developed for various psychological and psychiatric problems, including anxiety and psychosis [15-17]. Most of these VR interventions are therapist-led and include exposure treatment, cognitive behavioral therapy, cognitive training, skills training, and stress management. Over the past decade, several studies have tested stress-reducing VR interventions in clinical and nonclinical samples [17]. A VR program for patients with a stress-related psychiatric disorder showed that confrontation with emotionally charged VR objects improved relaxation and negative mood significantly more than conventional cognitive behavioral therapy [18]. A VR intervention combining roleplays with teaching stress management techniques in a natural VR environment reduced perceived stress in workers with high-stress jobs [19]. A systematic review of VR stress management interventions in the military found 14 small studies, showing that VR stress inoculation decreased perceived stress and negative emotions [20]. Several studies specifically investigated the effect of VR relaxation on stress levels, both in healthy volunteers and people with psychiatric problems, mainly using exposure to VR natural environments [17]. Immersion in VR nature showed improvement of perceived stress, affective responses, and physiological stress measures, to a greater degree than neutral VR environments or two-dimensional nature videos [21-26]. These results suggest that VR-based stress management, in particular immersive VR nature relaxation, is a promising approach for stress reduction that merits further clinical research [17,27]. To the best of our knowledge, no randomized controlled trials investigated the effects of VR nature relaxation as a self-management intervention for stress reduction in patients with a psychiatric disorder. We developed VRelax, a VR self-management relaxation intervention with high-quality 360-degree videos of natural environments and interactive elements that enhance relaxation and focused attention to the environments (see Methods). In this study, we investigated the immediate effects of VRelax on negative and positive affective states of patients receiving outpatient treatment for a psychiatric disorder.

We conducted a crossover randomized controlled trial comparing VRelax with standard relaxation exercises. To evaluate immediate effects, momentary levels of negative and positive affective states were assessed before and after each session. As secondary outcomes, short-term effects (after 10 days) were measured with questionnaires on global perceived stress and psychiatric symptoms (anxiety, depression, paranoia). We hypothesized that (1a) VRelax results in an immediate improvement of negative and positive affective states, (1b) VRelax has a short-term effect on global perceived stress and psychiatric symptoms, and (2) the immediate and short-term effects of VRelax are stronger than the effects of standard relaxation exercises.

This randomized crossover clinical trial found that VR relaxation immediately reduced negative affective states and improved positive affective states in patients who concurrently received ambulatory psychiatric treatment. VRelax had a stronger effect on negative affective states than standard relaxation exercises, in particular on feeling anxious, down, or cheerful. Psychiatric symptoms, measured over a 10-day period, improved somewhat in both conditions.

The results suggest that immersive VR nature exposure is an effective tool for immediate improvement of affective states and reduction of psychological stress, more powerful than conventional relaxation exercises for making people feel better. The standard relaxation exercises were audio tracks that participants played on their computer or smartphone. Some tracks included 2-dimensional nature pictures. Numerous VR studies have shown that immersion in a virtual environment and the experience of being in a different world strongly induce psychological and physical effects [40]. Although viewing 2-dimensional nature images and videos has previously also been related to stress reduction [41], the immersive nature experience of VR is likely to have contributed to the superior effect.

The immersive VR experience is likely to distract attention from negative thoughts and stimuli, as is found in VR pain distraction studies [42,43]. Attention restoration has been proposed as a key mechanism of health-promoting effects of nature exposure [44-46]. Attention fatigue occurs when, after prolonged and intense use, the capacity to direct voluntary attention is reduced, and the capacity to ward off negative internal or external distractions is reduced [47]. The salient and pleasant characteristics of natural environments capture attention automatically and effortlessly, enabling recovery of voluntary, cognitively directed attention [11,48]. Another potential mechanism originates from psycho-evolutionary theory, stating that exposure to natural environments rapidly restores positive affect and reduces stress-related physiological activation because in earlier times, rapid recovery of stress increased chances of survival [49]. In both theories, nature exposure leads to positive affect and stress reduction, in accordance with the results that were found in the present study.

The effect of VR relaxation was not so strong on global perceived stress over the past 10 days. The perceived stress measure in this study included other aspects of psychological stress besides negative affective states, such as level of perceived control over things that happen, confidence to cope with problems, and ability to overcome difficulties [33]. Whereas affective states are sensitive to immediate and short-term changes [32], the cognitive and behavioral components of stress are likely to change more gradually. Optimal duration of VR relaxation for this purpose may be longer than 10 days, or the study period may have been too short to capture such changes.

Capturing and keeping attention is likely to be more difficult in patients with psychiatric disorders than in healthy individuals because vigilance is impaired and their cognitively directed attention is more severely fatigued [50]. Feedback of psychiatric inpatients during the prototyping phase of VRelax suggested that repeated passive viewing of calm, uneventful virtual nature environments was not always sufficient to distract from negative thoughts and feelings. We therefore added interactive elements to some of the videos, (ie, a relaxation exercise, a simple game of air bubble popping, and musical tones played in response to head movements). Indeed, in this study, the VRelax log files showed that the interactive videos were used longer and more frequently than the “passive” videos.

There was one notable exception: scuba diving with wild dolphins had the highest number of visits. The popularity of the dolphin video can be explained by several factors. Throughout the 7-minute video, there is a lot to be seen all around, with more than 20 active dolphins constantly moving, which may have created a stronger sense of immersion than the other videos. In addition, health-promoting effects on humans have been ascribed to dolphins. Dolphin-assisted therapy is offered for a range of physical and psychological problems, including autism and depression, albeit scientific evidence for efficacy is limited and debated [51,52].

Participants did not report many problems with the use of VR. Only 2 patients stopped using VRelax because of cybersickness, and SSQ scores were low after the intervention. It has been suggested that patients with a psychiatric disorder may experience increased psychiatric symptoms when using VR [16,53]. This may be caused by challenging VR content such as exposure to anxiety-evoking stimuli, which was not part of VRelax. Another potential cause of anxiety and paranoia may be that wearing a head-mounted display disconnects people from their real environment. These issues did not occur during the study, perhaps because participants used VRelax in the safe environment of their own home.

Strengths of this study include the randomized crossover design. Participants served as their own control, minimizing the impact of confounding factors. Analyses of temporal effects suggest carry-over effects of both interventions. Effects on primary and secondary outcomes were stronger in the second intervention period than in the first. However, the impacts of carry-over or period effects on the results of the study are likely to be small because participants were randomized in a 1:1 ratio for order of interventions, and analyses of the primary outcome were adjusted for order of interventions. As a consequence of the crossover design, it was not possible to investigate the effects of VR relaxation on medium- or long-term outcomes. It is conceivable that VR experiences have a longer-lasting impact than standard relaxation exercises because of the immersive character, or simply because people may find it easier to keep using VRelax than to keep doing relaxation exercises. We did not observe such a pattern during the short duration of this study.

Patients used the interventions multiple times over a (double) 10-day period, with effect measures before and after each session. These frequent assessments and detailed longitudinal data increased real life ecological validity and reliability of the primary outcome measure and increased statistical power of the study. A disadvantage was that patients had to reflect on their affective state immediately after relaxation sessions, which may have reduced the beneficial effects to some extent.

Another limitation is that we did not measure physiological effects of VR relaxation, which would have been a valuable outcome measure and a possible way to study biological mechanisms of VR nature exposure. Relaxation therapy, as well as nature exposure, has been related to changes in physiological stress parameters, such as vagal tone, electroencephalography alpha and theta waves, heart rate variability, blood pressure, gene expression, and cortisol level [54,55]. Recent research of VR nature videos found that electroencephalography event-related potentials may be used as a marker of attention restoration [56].

If the results of this trial are replicated and extended, VR nature exposure may provide an effective relaxation intervention to support and enhance psychiatric treatments. Stress management is a cornerstone of psychiatric therapies, but there is a dearth of effortless, pleasant, and powerful self-management tools for improvement of affective states and reduction of stress. Longer-term effects of VR relaxation on perceived stress, psychiatric symptoms, and relapse prevention should be investigated, as well as cost-effectiveness. In addition, integration of biofeedback and more interactive elements (eg, breathing exercises) may increase efficacy of VRelax. Finally, a broader use of VR relaxation can be envisioned for people in need of distraction, for example, during unpleasant medical interventions, during long isolated hospital stays, or for bedridden (terminally) ill patients. VR applications are rapidly growing and may have a profound impact on the landscape of mental health interventions.