Testing the Effectiveness of a CBT Online-based Program to Reduce Suicide Ideation Among School Adolescents in Chile: A Cluster Randomized Controlled Trial

1. Study design. This is a single-blind, two-armed randomized controlled trial evaluating changes in primary and secondary outcomes post-intervention and follow-up. The two arms will be: 1) The intervention, which comprises eight internet-based modules of CBT delivered over 10-week, and four 45-min face-to-face psychotherapeutic CBT sessions; and 2) Control group (Treatment-As-Usual).
2. Participants. Schools with secondary education (Grades 9-12), mixed-sex, located in three different cities in the South of Chile (Talca, Linares, Curicó) with three classes per year.
3. Sample size. It is expected to recruit at least ten schools per arm, allocated on a 1:1 ratio. Each arm should include 140 eligible students. This sample size takes into account a loss at follow-up of 20% of the students. Considering a 20% of school rejection at the recruitment stage, it is expected to recruit 12 schools. Studies of similar school-based interventions report effect sizes of at least 0.4 standard deviation using symptoms questionnaires as proposed here. The results previously observed by Hetrick and colleagues and the clustersampsi command in Stata Software will be used to estimate the number of clusters in two arms, using the following command: clustersampsi, samplesize mu1(X1) mu2(X2) sd1(Y1) sd2(Y27) m(Z) rho(R). Where X1 = mean in arm 1; X2 = mean in arm 2; Y1 = standard deviation (SD) in arm 1; Y2 = SD in arm 2; Z = number of children per school on average (harmonic mean) (n = 14); and R = intracluster correlation. The two arms will be balanced for school size.
4. Process

4.1. Recruitment. The potential participants will be schools with secondary education from three cities in Chile. The schools will learn about the study through invitations that will be made to their institutional email and social networks. Eligible schools will be invited through letters sent to the authorities who will sing a letter to participate in the study.

4.1.1 Enrollment Strategy. This research project will be disseminated after the approval of the Scientific Ethics Committee. At the beginning of the academic year, a letter with information about the study and the written consent will be sent to all parents or main caregivers. To select the participants, all students attending to 9-12 Grades will be invited to participate in the study, and the students will be asked for a written assent. All consented/assented students will be surveyed with screening questionnaires during the second month of the academic year (C-SSRS, PHQ-9; CAPE-P-15). All students attending 9-12 grades in selected secondary schools and scoring > 3 points in the Columbia Severity Raging Scale (CSSR-S) will be invited to participate in the study. From previous data, it is expected to find 10% of students with suicidal thoughts. Students with intellectual disabilities and communication difficulties due to language will be excluded. Students with one or more suicide attempts during the last month (>11 on the PHQ-9 scale) and students with psychotic symptoms (>1.50 in the CAPE-P-15) will be also excluded. These students will be referred to Primary Care Centers and will be invited to use the intervention "Take care of your mood" ("Cuida Tu Ánimo; a universal intervention that shows beneficial effects for the prevention of depressive symptoms) available for free at the following link (http://cuidatuanimo.net), where students will find helpful information to prevent depressive symptoms. This intervention has been developed by a research team with whom Dr. Daniel Nunez collaborates.

4.1.2. Informed consent will be requested from students. The students of the selected schools will be invited to participate in informative talks about the study. Once the study, inclusion and exclusion criteria have been explained, a description of the screening instruments, their importance, and the selection process will be provided to interested parties. The informed consent will be sent to those accepting participate by emails and signed digitally through Qualtrics. Qualtrics is a platform that allows information to be collected online, with high-security standards, and that also can facilitate the digital signature through a cell phone or tablet (using the finger) or through a computer (with a mouse). This platform will collect data of screening instruments: suicidal ideation (SI) and suicide attempts, depressive symptoms, and psychotic symptoms. These data will be used for the study eligibility analysis. All who report any level of SI during the previous month (score > 3 in the C-SSR) will be invited to participate in the following step of the study.

Informed consent will cover both general screening and baseline measurements and follow-up during and after the intervention.