Pilot Study of the Acceptability and Feasibility of an 8-week Online Mindfulness-Based Cognitive Therapy Programamong Undergraduate Students: a Randomized Controlled Trial

1. Study design This is an experimental type study, with a randomized controlled trial design, with a control group in the waiting list mode. The intervention is an synchronous online mindfulness training, lasting eight weeks for university population.
2. Participants:

The participants will be undergraduate students from the Universidad de los Andes, studying from 2nd to last year, of different careers. 3. Sample size Although this is a pilot study, with the main focus on determining the acceptability and feasibility of a preventive intervention based on mindfulness, a sample calculation is carried out in order to explore the efficacy of this intervention under controlled conditions such as those proposed in this draft. For this calculation, the intensity of depressive symptoms is considered as the main response variable or primary outcome. We will use an effect size of big nature (Cohen's d = 0.8), similar to that found in other pilot studies that evaluated similar interventions. Considering a statistical power of 0.80 and an alpha of 0.05, and according to a two-tailed hypothesis test, we will need 26 participants per group (52 in total). Considering that we expect a loss of about 20% of the participants, the minimum number to recruit in the proposed study will be 62 (31 per group). The intervention proposed in this study can be applied remotely to a maximum of 20 students, so the students will be separated into 2 subgroups that will do the intervention in parallel, for 8 weeks. 4. Process

4.1. Recruitment The potential participants will be undergraduate students from the Universidad de los Andes, who meet the inclusion and exclusion criteria previously described. They will learn about the study through invitations that will be made to their institutional email and social networks, by the research team, to carry out the study instruments and having signed an informed consent.

4.1.1 Enrollment Strategy This research project and the mindfulness intervention will be disseminated after the approval of the Scientific Ethics Committee, during the first weeks of the second semester of 2021. It will be disseminated via personal email with the relevant information of the study, in addition a cycle of informative talks ("Seminars"), whose link will be sent via email. The talks will inform about the duration, requirements, benefits, risks of participating in the study. These talks will be conducted by the mindfulness instructors, having total privacy of what is discussed in them. Once the meeting is over, interested persons will be invited to sign the informed consent, fill out the screening instruments and leave their contact information to participate in the intervention. Through these screening instruments, it will be possible to identify students who meet inclusion and exclusion criteria. Students who meet the inclusion criteria will be contacted and the group they belong will be informed according to the randomization procedure. Those students who have a score of ≥15 points on the PHQ-9 scale will not be able to participate in the intervention, and they will be invited to use the intervention "Take care of your mood "(universal intervention that shows beneficial effects for the prevention of depressive symptoms) available for free at the following link (http://cuidatuanimo.net), where you will find useful information to prevent depressive symptoms. This intervention has been developed by a research team with whom Dr Jorge Gaete collaborates. Additionally, they will also be invited to request help in the Unit of Wellbeing of University Life at Universidad de los Andes. This group of students will be contacted by the research team, a week, and 2 weeks after having answered the screening instrument to find out if they requested an appointment with the University Wellbeing team.

4.1.2. Informed consent Informed consent will be requested from students. The students of the Universidad de los Andes will be invited to participate in an informative seminar about the study. Once the study, inclusion and exclusion criteria have been explained, the exhibitor will provide interested parties with a description of the screening instruments, their importance and selection process. If they accept to participate, the informed consent will be sent to the emails, which will be signed digitally through Qualtrics (A platform that allows information to be collected online, with high-security standards and that also has the ability to facilitate the digital signature through a cell phone or tablet (using the finger) or through a computer (with a mouse), and also the screening instrument that will evaluate: sociodemographic data, depression, anxiety and stress, mindfulness skills, physical and psychiatric comorbidities, prior consultations to mental health services, medications, alcohol and drug use, previous practice of mindfulness, quality of life. These data will be used for the study eligibility analysis. Those who meet the inclusion criteria will be enrolled in the study and they will be randomly distributed in the intervention group and the control group.