Efficacy of a mindfulness-based intervention programme with and without virtual reality support to reduce stress in university students: protocol for a randomized controlled pragmatic trial

Background There is growing concern about mental health problems in university students. For this reason, mindfulness training is becoming increasingly popular in university settings. However, mindfulness-based interventions (MBIs) usually present high attrition rates. This trial aims to evaluate the efficacy of a MBI to reduce perceived stress and to improve the psychological well-being of university students, as well as to explore the capacity of virtual reality (VR) to enhance adherence to the intervention. Methods This study protocol presents a randomized controlled trial (RCT) involving assessment time points of baseline, posttreatment and 6-month follow-up. A total of 280 students from the Spanish National Distance Education University (UNED) or the University of Zaragoza will be randomly assigned to a mindfulness condition, a mindfulness condition complemented by VR, and a relaxation condition to serve as a control group. Stress will be the main outcome and will be measured using the 10-item self-report Perceived Stress Scale (PSS). Other well-being and academic functioning outcomes will be assessed, as well as variables that explore the impact of VR. Multilevel mixed-effects models will be calculated to estimate the efficacy of the programme, and effect size estimations will be carried out. Effects of VR in adherence to programme will be evaluated. Discussion Some strengths of this study are the RCT design, which includes a suitable active control group and a 6-month follow-up assessment; a large sample size of university students at different stages of their courses and a variety of degrees; and the incorporation of the VR support to facilitate completion of the MBI programme. Potential limitations are the voluntary participation of the students and the utilization of self-report measures. Trial Background


Abstract
Background There is growing concern about mental health problems in university students. For this reason, mindfulness training is becoming increasingly popular in university settings. However, mindfulness-based interventions (MBIs) usually present high attrition rates. This trial aims to evaluate the efficacy of a MBI to reduce perceived stress and to improve the psychological well-being of university students, as well as to explore the capacity of virtual reality (VR) to enhance adherence to the intervention. Methods This study protocol presents a randomized controlled trial (RCT) involving assessment time points of baseline, posttreatment and 6-month follow-up. A total of 280 students from the Spanish National Distance Education University (UNED) or the University of Zaragoza will be randomly assigned to a mindfulness condition, a mindfulness condition complemented by VR, and a relaxation condition to serve as a control group. Stress will be the main outcome and will be measured using the 10-item self-report Perceived Stress Scale (PSS).
Other well-being and academic functioning outcomes will be assessed, as well as variables that explore the impact of VR. Multilevel mixed-effects models will be calculated to estimate the efficacy of the programme, and effect size estimations will be carried out.
Effects of VR in adherence to programme will be evaluated. Discussion Some strengths of this study are the RCT design, which includes a suitable active control group and a 6month follow-up assessment; a large sample size of university students at different stages of their courses and a variety of degrees; and the incorporation of the VR support to facilitate completion of the MBI programme. Potential limitations are the voluntary participation of the students and the utilization of self-report measures. Trial registration number ClinicalTrials.gov NCT03771300. Background 4 The mental health of university students is a noteworthy concern nowadays. Nineteen institutions of higher education across eight countries (Australia, Belgium, Germany, Mexico, Northern Ireland, South Africa, Spain, United States)participated in a project with the aim of estimating prevalence of common mental disorders among first-year college students, and found that 35% of the 13,948 respondents screened positive for at least one of the common lifetime disorders assessed and 31% screened positive for at least one 12month disorder (1). Other similar studies indicate a high prevalence of psychological distress, anxiety and depression among university students (2)(3)(4) and even a high prevalence of suicidal thoughts and autolytic behaviours (5). Universities are thus challenged to set up effective preventive interventions in order to help students cope better with university life and improve their mental health. In this regard, a meta-analysis confirmed that cognitive, behavioural and mindfulness-based interventions are effective in reducing symptoms of anxiety in university students (6).
Mindfulness-based interventions (MBIs) are defined as a type of intervention whose main aim is to train the mind to adopt a non-judgemental present-focused awareness (7). In recent years, these interventions have been expanded and have proven to be effective for a variety of clinical and non-clinical populations (8)(9)(10). This expansion has allowed the benefits of mindfulness practice to be studied in university students (11)(12)(13)(14)(15). For instance, a recent study (16) with a large sample of 616 students from the University of Cambridge (UK) showed that the Mindfulness Skills for Students (MSS) programme reduced selfreported psychological distress in university students during the examination period compared to a group of support as usual, showing moderate effects.
The present study pursues the testing of this evidence in the Spanish context, while exploring the potential benefits of virtual reality (VR) when combined with the provision of mindfulness training to university students. The effectiveness of VR has been shown for the treatment of several psychological disorders, particularly anxiety disorders (17).Furthermore, current research has found promising results when it is incorporated into 'third wave psychotherapies' such as MBIs, although there is still only a relatively limited number of studies available (18). A recent study found a high acceptability of VR for the practice of mindfulness exercises, together with a significant increase in mindfulness state and an improved emotional state after only one VR mindfulness session in experienced meditators (19). It has recently been found that VR might enhance adherence to mindfulness programmes in patients suffering from generalized anxiety disorder (20). In general, MBIs suffer from important attrition rates (10,21) and failure to consolidate practice habits might undermine possible benefits (22). The implementation of additional VR scenarios into the practice of mindfulness exercises could be well-accepted and useful among university students because of their high affinity with new technologies (23).

Objectives
In this context, the main objective of this study is to evaluate the efficacy of an MBI program to reduce stress in university students, in comparison with an active control group undertaking relaxation therapy, which has shown some evidence to reduce stress in this population (24)(25)(26)(27). Other exploratory aims are as follows: (1) to analyse the efficacy of an MBI program for the improvement of psychological well-being and academic functioning, as well as dispositional mindfulness and self-compassion, in university students, in comparison with the active control group treated with relaxation exercises; (2) to evaluate whether there are differences in the adherence to practice in the mindfulness programme, according to the modality in which this mindfulness intervention has been applied (i.e. with or without VR support); (3) to examine the possible differential effectiveness of each of the mindfulness subgroups (i.e. with or without support of the VR) in comparison with the active control group treated with relaxation therapy; (4) to assess the effects of different mindfulness-based VR environments on the emotional and mindfulness states of university students, as well as to evaluate the sensation of immersion in the landscapes created by each VR environment.
Our main hypothesis is that the provision of mindfulness training will reduce perceived stress in university students to a greater extent than with relaxation training.

Trial design
This is a three-arm, parallel randomized and controlled, pragmatic superiority trial, involving three assessment time points (baseline, posttreatment and 6-month follow-up).
University student participants will be randomly assigned to three different intervention groups: mindfulness, mindfulness + VR, and relaxation therapy. The overall design and flow chart of the study can be seen in Figure 1. This protocol was designed in accordance with the SPIRIT 2013 statement (28).The study protocol was retrospectively registered (December 2018) in the web of controlled studies (ClinicalTrials.gov NCT03771300).

Methods
Setting, eligibility criteria and recruitment Participants will be recruited from two Spanish universities in the province of Zaragoza (Spain). The participants will be students of the University of Zaragoza or the National Distance Education University (UNED), who will be recruited according to the following criteria: (a) ≥ 18 years of age; (b) enrolled in undergraduate or master's degree courses at these universities; (c) enrolled in the faculties of social sciences or health sciences at the Zaragoza campus (in the case of University of Zaragoza students) or at the Calatayud campus (in the case of UNED students); (d) speaking and writing Spanish language; and (e) providing written informed consent before knowing the assignment group. The exclusion criteria will be as follows: (a) suffering from a disease affecting the central nervous system (CNS); (b) presenting with a diagnosed psychiatric condition or serious psychiatric illness; (c) consumption of drugs or medication that could affect the CNS; and (d) having a disorder or illness that may affect their mood. The person in charge of the project will carry out individual interviews with the participants in order to ensure compliance with the inclusion criteria, as well as to ensure that none of the exclusion criteria is present in the participants. According to the pragmatic nature of the study, concomitant care or interventions will be permitted during the trial.
Students will be recruited through the following three main procedures: (1) informative posters will be put up in university buildings containing a brief explanation of the study and the contact details; (2) several members of the university teaching staff will contact their students and send them an informative e-mail with a brief explanation of the study and the contact details; (3) different tuition centres, student organizations and support services for university students will also send their users an informative e-mail with a brief explanation of the study and the corresponding contact details. Figure 2 shows the schedule of enrolment, interventions, and assessments.

Sample size
The sample size has been estimated taking as a reference a moderate difference (d = 0.40) between the total MBI group and the active control group in the main variable of perceived stress (Perceived Stress Questionnaire -PSS), as it has been observed in previous similar studies (29), accepting an alpha of 0.05 and a beta risk of 0.20 in a bilateral contrast, with a 2:1 allocation rate (so that two participants will be assigned to the mindfulness total group -one in the condition of VR support and another in the condition that does not have such support -for each control subject). This unequal randomization ratio design was established to gain additional exploratory information on the use of VR when added to the mindfulness treatment proposed (30,31).Therefore, and under these circumstances, 225 participants will be required: 75 participants in the active control group of relaxation therapy, and 150 participants in the total MBI group. Taking into account all the participants, and assuming an attrition rate of around 25% (21), the total sample has been established at 280 university students.
Randomization, allocation and masking of study groups The assignation of the subjects will be carried out after the baseline evaluation by a member of the research group, who has no knowledge about the study aims, through a simple random sequence generated by computer. Participants will be randomized into three groups ('mindfulness', 'mindfulness + VR', and 'relaxation'), considering the secondary objective of evaluating the effectiveness of each mindfulness subgroup separately. Nevertheless, taking into account the primary aim of isolating the common effects of both mindfulness subgroups, 'mindfulness' and 'mindfulness + VR' will work as an only one group of treatment. Posttreatment and 6-month follow-up measurements will be recorded by a different and independent assessor who will be blind to the study condition of participants. However, due to the characteristics of the intervention, providers and participants will be able to know what kind of intervention they are offering and receiving respectively, so this will be a single-blind study although all the participants will be treated through suitable active conditions. Interventions Within the three conditions described below, motivational techniques will be used to increase adherence of participants to sessions and daily tasks. The participants will not receive any amount of economic compensation. In order to improve the adherence of participants to sessions, they will be sent reminders via WhatsApp of the start time of the session, a few hours prior to each session. Daily tasks aids, such as mindfulness or relaxation exercise audio recordings (depending on the condition) will also be sent through a weekly WhatsApp message in each group. All participants will be encouraged to do a daily task at home and will be asked to keep a daily written record of the number and duration of practice sessions.
-Mindfulness condition: In this group, n = 93 students will be participating in a programme structured around two central elements, mindfulness and compassion. The programme consists of 90-minute group sessions, held once a week over a space of 6 weeks, and is offered as an extra-curricular activity. Each sub-group of mindfulness condition will be formed by 15 or 16 participants, so there will be six sub-groups of this condition. The sessions combine components of theory and practice, using a methodology which prioritizes inquiry, reflection and debate among the group of students. The theory component will comprise mindfulness and compassion concepts set out over the length of the programme, in addition to others related to time management, stress, anxiety and the balance between personal life and academic/work life. The practical component of the program will consist of formal and informal mindfulness and self-compassion exercises under the guidance of a psychologist, who will be specifically trained in the application of the theoretical and practical components of the mindfulness programme to university students. Table 1 provides a summary of the structure and contents of the mindfulness programme by session. This short VR session is designed on an individual basis and consists of a mindfulness or self-compassion exercise through VR. The VR kit comprises a set of Samsung GEAR VR goggles, a Samsung Galaxy S6 phone and optional headphones (https://www.psious.com/).
The content and objectives of each VR scenario are specified in Table 2. In this condition, the mindfulness instructor will remain the same but the implementation of VR will be carried out by another psychologist who is specifically trained in the application of VR scenarios. Prior to the use of VR, the psychologist will check the participants' health. In general terms, the use of VR is not recommended for pregnant women; people suffering from hypertension, ear infections, epilepsy or vertigo; patients who have recently undergone surgery; or people who suffer from cardiovascular disease, psychosis or serious mental illness. For this reason, the psychologist will ensure that none of these conditions are present. The participant will be seated on a chair in a quiet and secure place. visualizations, as it was originally proposed by Jacobson (33). Table 3 provides a summary of the programme structure and contents. All participants in this condition will be instructed by a psychologist specifically trained in the application of progressive muscle relaxation therapy.
Outcomes and data collection Several outcomes will be measured and compared between the mindfulness (with and without VR support) and control groups. We will collect data on socio-demographic variables and experience in the use of new technologies (baseline), as well as on the primary and secondary outcomes (baseline, posttreatment and six month follow-up). The study primary outcome will be perceived stress. Secondary outcomes will be psychological wellbeing (e.g., anxiety, affectivity and emotional regulation), academic functioning (e.g., academic engagement, academic burnout and burnout clinical subtypes) and trait mindfulness and self-compassion. Other secondary VR measurements will be emotional intensity, state of mindfulness and sense of presence. All the measurements will be collected using paper-and-pencil surveys. In the last session, participants of all the groups will be called for a meeting to complete the posttreatment questionnaires. Participants who did not attend this meeting will be sent a message via WhatsApp, in which they will be informed about two possible dates to complete the questionnaires. Six months later, a similar strategy to complete the follow-up-intervention questionnaires will be used (all the students will be called for a meeting via WhatsApp). Participants who did not attend this meeting will be sent a new message with two possible dates. No outcome data will be collected for participants out of the referred meetings. Acceptability of the intervention will be measured using an adapted version of the Credibility/Expectancy Questionnaire (36,37).Participants will complete this scale before and after the intervention. The adapted questionnaire comprises 6 items rated from 0 ('not at all') to 10 ('very much'), with appropriate psychometric properties (34,35).

-Primary Outcome
Perceived stress, measured by the 10-item self-report PSS (38,39), will be the primary outcome. Through the PSS, participants will be asked to rate how unpredictable, uncontrollable and overloaded they have found their life over the past month on a 5-point Likert-type scale (from 0 = 'never' to 4 = 'very often'). Higher scores indicate higher levels of stress. The Spanish PSS40)provides a reliable and valid measure of perceived stress, with adequate psychometric properties (α = 0.82, test-retest, r = 0.77).

-Secondary Outcomes
Anxiety will be measured by the State-Trait Anxiety Inventory (STAI) (41)(42)(43). This inventory is a widely used, validated measure of anxiety and consists of 20 statements that evaluate how the participants feel at the present moment (state anxiety), and 20 statements that evaluate how the participants feel in general (trait anxiety). It uses a 0-3 Likert-type rating scale -the higher scores indicating greater anxiety levels -with good psychometric properties (α = 0.93) in university students (44).
Positive and negative affect will be measured by the Positive and Negative Affect . Emotional regulation will be measured by the Emotional Regulation Questionnaire (ERQ) (47).This 10-item scale has been designed to measure respondents' tendency to regulate their emotions in two ways: cognitive reappraisal (6 items) and expressive suppression (4 items). Participants respond using a 7-point Likert scale (from 1 = 'strongly disagree', to 7 = 'strongly agree') where higher scores indicate increased use of regulatory strategies.
The Spanish version of the ERQ shows adequate internal consistency, test-retest reliability, and convergent and discriminant validity, with reliability values of α = 0.79 for reappraisal and α = 0.75 for suppression (48). Self-compassion will be measured by the Self-Compassion Scale (SCS) (51) Spanish version (52). This 26-item questionnaire assesses the components of self-compassion across three facets: self-kindness, common humanity and mindfulness. Higher scores indicate greater levels of self-compassion. The facet scores can be combined to produce a total self-compassion score (53). The SCS uses a 5-point Likert scale, ranging from 1 ('almost never') to 5 ('almost always'). The Spanish version has demonstrated to be a valid and reliable instrument (α = 0.87; test-retest = 0.92).
Academic engagement will be measured by the Utrecht Work Engagement Survey Scale-Students (UWES-S) (54). This 17-item questionnaire includes three subscales: vigour (6 items), dedication (5 items) and absorption (6 items). The UWES is scored on a sevenpoint frequency Likert-type rating scale varying from 0 ('never') to 6 ('always'). Higher scores in each subscale indicate greater levels of engagement. The UWES Spanish version has demonstrated to have good psychometric properties (54).
Academic burnout will be measured by the Maslach Burnout Inventory Student Survey (MBI-SS) (54), where the references to work have been changed for references to study. This 15-item questionnaire includes three subscales: exhaustion (5 items), cynicism (4 items) and efficacy (6 items). High scores in exhaustion and cynicism, and low scores in efficacy are indicative of burnout. Participants have to respond on a Likert-type scale with 7 options ranged from 0 ('never') to 6 ('always'). The psychometric properties of the MBI-SS Spanish validation have been observed to be adequate (54).

Burnout clinical subtypes will be measured by the 36-item Burnout Clinical Subtype
Questionnaire (BCSQ-36) (55), which assesses the three following burnout subtypes: frenetic, under-challenged and worn-out. References to work will be changed to references to study. Each subscale comprises 4 items. Participants indicate the point to which they agree with each item using a Likert-type scale with 7 options ranging from 1 ('never') to 7 ('always'). Higher scores mean greater levels of burnout subtypes. The BCSQ-36 has demonstrated good psychometrics in the Spanish population (55).

-Virtual Reality measurements
A visual analogue scale (VAS) (56) will assess the intensity of different emotions before and after the VR intervention. A briefer version of the original measure (16 emotion items) will be used and it will be composed by 7 emotion items (happiness, sadness, anger, surprise, anxiety, relaxation/calm, vigour/energy). Participants can choose responses ranging from 1 ('not feeling the emotion at all') to 7 ('feeling the emotion extremely'). This 7-item scale has been successfully used in previous studies (19,57).
State of mindfulness will be measured just before and after each VR session using an adaptation of the Mindful Attention Awareness Scale (MAAS-State) (58-60). Item numbers 3, 8, 10, 13 and 14, has been designated to assess state mindfulness (58), and will be included. Each item will be rated on a 7-point Likert-type scale, between 0 ('not at all') and 6 ('very much'). Higher scores reflect greater levels of state mindfulness. This shorter 5-item scale has been successfully used in previous studies (19).
Sense of presence in the VR scenarios will be measured just before and after each VR session, using 4 items with a 7-point Likert scale ranging from 1 to 7. These 4 items were adapted from the Slater, Usoh & Steed Questionnaire (SUS) (61). The Spanish version has been used to measure sense of presence provided by VR, with α = 0.92 (19).

Data monitoring and harms
The Data Monitoring Committee (DMC) of this trial is a group composed of five experts: the person in charge of the project, the head of the group, an independent clinical psychologist, an independent psychiatrist and the psychologist responsible of data handling. The DMC will meet three times throughout the trial (just before starting, in the midst of the intervention and at the end of the trial), in order to evaluate the possible cases of participants presenting adverse effects and to ensure that the trial is carrying out correctly. The practice of relaxation may have associated paradoxical increases in tension, relaxation-induced anxiety and panic and decreases in sympathetic tone which can lead to nausea and vomiting (62). Adverse effects of meditation can include psychological effects such as emotional stress, confusion, disorientation and dependence on practice; psychopathological effects such as anxiety, deliriums and hallucinations; and/or physiological effects such as pain, sensorial dysfunction, exacerbation of neuromuscular/joint diseases, reduction in appetite and insomnia (63).In a recent multi-cultural study on the effects of meditation, 25.4% of the participants reported unwanted effects, but most of them were transitory with no need for medical assistance (64). On the other hand, VR is associated with uncomfortable physical responses such as nausea (burping, increased salivation, etc.), oculomotor symptoms (eyestrain, difficulty concentrating, etc.) and disorientation (dizziness, vertigo, etc.) (65)(66)(67). Any adverse effect which is referred from the participants during the sessions, along the trial or observed by the psychologists in charge of the groups will be communicated to the DMC.

Data analysis
To report this randomized controlled trial (RCT) we will make use of the recommended CONSORT guidelines (68,69). Paper-based data entry will be double-checked revising possible out-of-range values. Socio-demographic data will be described at baseline by means of frequencies (percentages), medians (inter-quartile range) and means (SD), depending on the distribution of each variable. The treatment conditions will be compared to evaluate the success of randomization by means of chi-square (or Fisher when necessary), Kruskal-Wallis and one-way ANOVA tests, respectively. This strategy will also be used to analyse possible differences between groups in terms of preference for treatment conditions and credibility as a result of the treatment received.

-Main analysis
The efficacy of the general mindfulness programme -integrating both groups with and without the presence of VR support -compared to the relaxation control condition will be analysed according to the main PSS variable at posttreatment, which will be taken as a continuous outcome. It will be developed by means of a repeated measures design and an intention to treat (ITT) basis, by using multilevel mixed-effects regression models including time as an independent variable and subjects and presence/absence of VR support as random effect variables. For this, the restricted maximum likelihood (REML) estimation will be used, which produces unbiased estimates in case of small or unbalanced sample sizes (70). Non-standardized slopes and 95% confidence intervals (95% CI) will be calculated by adjusting the time of the year in which the programme was undertaken (temporality), and those socio-demographic variables that show significant differences between groups at baseline. The 'group x time' interaction will be considered in order to study the specific trajectories of each group throughout the intervention, and to determine whether the possible differences between the general mindfulness group and the relaxation group remain consistent over time. Effect size, as the differences between groups at post-test and at 6-month follow-up, will be assessed using Cohen's d statistic, calculated by the combined standard deviation in the pre-test, thus weighing the differences between the corresponding marginal means (71). Effect sizes are defined as small, when d ≤0.2; medium, when d = 0.5; and large, when d ≥ 0.8 (72).

-Secondary analyses
The efficacy of the general mindfulness programme -integrating both groups with and without the presence of VR support -compared to the relaxation control group regarding to the psychological well-being, academic functioning, trait mindfulness and selfcompassion outcomes, will be calculated following the same analytical strategy used for the main analyses. Moreover, the efficacy of each mindfulness subgroup (with or without VR support) vs the control group as regards the main and secondary variables will be estimated, although the mixed regression model in this case will only include subjects as a random effect variable. Per protocol analysis will be carried out, considering only those participants who attend at least ≥50% of the sessions (73,74). Sensitivity analysis will be developed to assess the effects of missing data, which will be replaced by multiple imputations based on chained equations as long as there are <40% missing data in the corresponding outcomes and whether missing values are distributed at random (MAR) to ensure validity (75). Additionally, possible differences in emotional state, immersion in the VR environment and state of mindfulness in the mindfulness + VR subgroup will be explored through each of the VR environments, using mixed models.
Baseline socio-demographic and psychological characteristics and the fact of belonging to subgroups (with or without VR support) will be evaluated dependent on compliance with the programme. Participants will be considered to have completed the programme when they have attended at least half or more of the sessions (73,74). The characteristics of the subgroups will be compared by means of the corresponding chi-square (or Fisher) tests, and the Student's t-test for unpaired groups.
No interim analyses before ending the study will be developed, unless DMC decided to prematurely terminate the study. An alpha level of 0.05 will be set, using a two-tailed test. The probability values relative to the main analysis will be adjusted according to Benjamini-Hochberg's correction for multiple comparisons. The secondary analyses will be considered as exploratory and thus they will not be corrected (76).

Discussion
Mental health of university students is being threatened as a result of the excessive pressure they are suffering to reach excellence, and that is manifest through high levels of stress (77). Thus, universities are being encouraged to provide preventive programmes for their students in order to improve their stress and mental health levels (6).
Mindfulness programmes are becoming a promising intervention in this regard, although there are several limitations across its research. Some of these limitations are the use of quasi-experimental or single-group research designs, small sample sizes, lack of follow-up measurements, and reliance only on self-report measures (78). The present study is the first RCT that will be developed in the Spanish context aiming to lower perceived stress in university students by using a MBI programme. It pretends to overcome some of the referred previous limitations, using a randomized controlled trial with a suitable active control group treated with relaxation exercises, a relatively large sample comprising of 280 university students in different years and degree courses, and a 6-month follow-up assessment. Nonetheless, participation of the students will be voluntary, and the only measures used will be self-report questionnaires.
To the best of our knowledge, this is also the first RCT to explore the possibilities of VR use as an adjunct to the mindfulness programme in university students. One of these possibilities could be the improvement of adherence rates to completion to the programme, as it has been observed in other different populations suffering from generalized anxiety (20). An important barrier MBI programmes entail is the requirement of certain amount of discipline in the practice of meditation exercises (22) and as a consequence they suffer from high rates of attrition (10). It has been clearly established that failure to consolidate practice may undermine benefits related to the MBI interventions (30,79). The attraction of new technologies such as VR produces to young people might favour completion to the programme in university students. Significant

Ethic statements
Written informed consent will be obtained from all individual participants included in the study before randomization. They will be provided with detailed information about the study and informed that they may leave the study at any time, but they will not receive any remuneration or special grades for participating in the study. This study has been approved by the Ethical Committee of Aragon, Spain (PI18/325). Any important modification of the protocol will be communicated to this committee. All procedures performed in this study involving human participants are in accordance with the ethical standards of the 1964 Helsinki Declaration or comparable ethical standards. The data will be treated anonymously and will only be used for the purposes of the study. The confidentiality of participants will be guaranteed before, during and after the trial and will be protected by the Organic Law on Protection of Personal Data (15/1999 of December 13, LOPD) and all relevant EU legislation on privacy and data protection. All study information will be confined in secure drawers with limited access. Electronic data files will be password-protected and secured via advanced encryption standard (AES-256). In cases of unexpected effects, the DMC will be responsible for ensuring anonymity. This trial will be performed in compliance with the study protocol and with good clinical practice guidelines with the main aim of protecting and preserving human rights (80). Publication authorship of the final trial report will be based on making substantial contributions according to publication scholarly work in medical journals (81).

Consent for publication
Not applicable

Availability of data and material
The study is currently in progress, in the stage of data recruitment. Consequently, it is not possible to share the data. Once available, the results of the trial will be presented at national and international conferences and in peer-review journal publications.
Anonymized data will be available on request under reasonable conditions.

81.
International Committee of Medical Journal Editors (ICMJE Note. This mindfulness programme has been designed by some of the authors of the present article. This exercise is set in a conscious walking environment an consists of two component exercises. In the first one, the participant instructed to focus attention on the visual channel, observing how the leave of a tree fall; if the mind is distracted, the participant is encouraged to brin attention back to the falling of the leaves of the tree. In the second exercise the participant is instructed to be aware of bodily sensations while observin a lemon.

2.-Body-scan exercise
The simulation of a human figure is used in this exercise Throughout it, different body areas of this figure are highlighted (by mean of blue bubbles) while the participant is instructed to become aware of th bodily sensations that correspond to each illuminated area. Therefore, th exercise consists of a guided body-scan with visual support. The huma figure is fixed and three-dimensionality is provided by the mountai landscape around the human figure.

3.-Conscious observation exercise
This exercise is set in a spring landscape. The participant will b asked to focus attention on several elements of the natural landscape whil walking. When the participant arrives at a bonfire, he/she will be explaine the concept of the 'figure of the observer of thoughts': observing one's ow thoughts without being trapped by them. At the end of this exercise, th camera will move away to ask the participant to observe the landscape from the new perspective.

4.-Breathing in exams
This exercise helps to find calm and serenity in a difficult situatio such as an examination. The participant is immersed in an exam situatio taking place at the university. Before doing the exam, the participant invited to hear a 5-minute breathing exercise audio recording. When finishes, the participant can do the exam using a virtual tablet.

5.-Compassionate coping in a difficult situation
The first part of this exercise is based on identifying and recreatin a life situation in which the participant has experienced a negative emotion In the second part of this exercise, the participant is instructed to accept an let go of the emotion which has emerged from this difficult situation Dolphins swimming work as a metaphor for letting go of the negativ emotion.

6.-Gratitude exercise
This exercise is set in a desert scenario. It is the shortest exercis and is based on 1) identifying and being aware of three positive aspects o the participant's life and 2) showing gratitude for them. These three aspect are represented by three geometric figures located in the landscape. Th exercise develops the concept of 'loving kindness'.
Note. Each exercise has been carefully selected from a large list of mindfulness practices developed by professionals with extensive experience in the field of mindfulness to make sure that each RV session corresponds to the contents provided in each group session and supports the learning of the session.

Session
At the beginning of the session Exercises 1 -Group introductions and presentation of the objectives -Basic principles of progressive muscle relaxation -Systematic tension and release of 16 muscle groups -Progressive muscle relaxation exercise with 16 muscle groups -Imagination training 2 -Sharing experience of daily tasks -Visualization techniques -Progressive muscle relaxation exercise with 16 muscle groups -Orange exercise(visualization) 3 -Sharing experience of daily tasks -Systematic tension and release of 7 muscle groups -Progressive muscle relaxation exercise with 7 muscle groups -The beach exercise(visualization) 4 -Sharing experience of daily tasks -Progressive muscle relaxation exercise with 7 muscle groups -Landscape exercise(visualization) 5 -Sharing experience of daily tasks -Systematic tension and release of 7 muscle groups -Progressive muscle relaxation exercise with 4 muscle groups -The globe and white light exercise(visualization) 6.
-Sharing experience of daily tasks -Relaxation through recall -Relaxation through recall -Mental relaxation and 'the perfect day 'exercise (visualization) Note. Adapted version proposed by Bernstein and Borkovec (1973) of the Progressive Muscle Relaxation. Figure 1 Flow chart of the study Figure 2 Schedule of enrolment, interventions, and assessments