## 3 Results
### Study Results
#### 3.2.8 Main Findings and Limitations  
Nine studies indicated a significant positive effect of VR interventions either on perceived stress [52; 54; 55] and anxiety state [47; 57; 59] or on their participants' emotions [48; 49; 56]. Among these studies, two studies improved, nevertheless, subjective scores in the control condition apart from those in intervention groups [54; 59]. Moreover, in their study, [PERSON] et al. [53] induced greater subjective arousal reduction in the control VR biofeedback (BF) placebo group than in the VR respiratory BF group. However, five studies did not report an effect of the VR intervention on stress-related questionnaires [31; 46; 50; 51; 58]. Lastly, [PERSON] and [PERSON] [35] showed a significantly higher decrease in state anxiety among participants in video- than in VR- and audio-guided sessions. On physiological levels, it was indicated that VR treatments had a significant positive effect on cardiac activity [35; 46; 50; 56; 58; 59]. Furthermore, [PERSON] et al. [31] showed a reduction in cardiac activity in VR conditions and a control group. On the other hand, salivary cortisol decreased only in VR conditions, as concerns the same study. [PERSON] et al. [53], in their study, obtained a significant improvement in cardiac and brain indices only in the control VR-BF-placebo condition. Moreover, stress level evaluated by the EEG measurements decreased effectively in the study of [PERSON] et al. [57]. Electrodermal activity quantified by skin conductance level decreased in three studies [46; 49; 51; 57]. Lastly, four studies did not report a significant effect of VR on stress-related physiological parameters [47; 48; 54; 55]. However, [PERSON] et al. [50] showed reduced muscle activity among participants in the biofeedback condition, which did not involve VR. As regards the dimension of user experience, the studies included in the current review reported a positive experience overall. In detail, [PERSON] et al. [46] showed a higher mood impact and scene quality in both natural environments. Furthermore, the respondents agreed that one would benefit from VR technology and it could enhance people's relaxation ability. In the study of [PERSON] et al. [48], participants indicated their preferences for an open space environment with prominent water elements and some greenery. In their experiment, [PERSON] et al. [49] showed a positive experience with VR overall. They reported, however, symptoms related to VR exposure, such as slightly blurred vision and mild nausea. [PERSON] et al. [51] indicated a higher sense of general presence and experienced realism in video than in slideshow conditions (\(p<0.001\), \({\eta_{\text{p}}}^{2}>0.30\)). Furthermore, the participants indicated high sense of spatial presence in videos and in the forest environment (\(p<0.01\), \({\eta_{\text{p}}}^{2}>0.20\)) as well as high involvement in forest scene videos(\(p<0.001\), \(\eta_{\text{p}}{}^{2}>0.50\)). Although the feeling of presence was high, the respondents reported increased symptoms of simulator sickness. In the studies of [PERSON] et al. [54] and [PERSON] et al. [55], the participants assessed their general VR experience as positive and, also in terms of comfort and immersion. Lastly, [PERSON] et al. [58] described a higher level of connection with biophilic elements than with natural analogue components. Nonetheless, only [PERSON] et al. [52] reported a tendency showing that people who experienced VR might have had a higher sense of presence compared to the control condition (i.e., conventional relaxation video). In this review, 75% of the included studies indicated possible limitations of their research work [31; 47; 55; 56; 57; 58; 59; 55; 57; 59].