Esther Mertens

| 117 Components of School-Based Interventions regular school hours, targeting all students (Mychailyszyn et al., 2012; Peters et al., 2009). The intrapersonal domain was defined as feelings, emotions, and attitudes about the self (Barber, 2005) consisting of competencies (e.g., resilience, self-esteem, self-regulation, general wellbeing) and problems (e.g., internalizing behavior). The interpersonal domain was defined as the ability of an individual to build and maintain positive relationships with others and understanding social situations, roles and norms (Shek & Leung, 2016) consisting of competencies (e.g., social competence, sexual health, positive school climate) and problems (e.g., aggression, bullying). Studies were eligible for review when (1) the intervention was implemented in a regular school (i.e., not in special education), (2) the intervention was implemented during regular school hours in a group setting, (3) the intervention was aimed at improving (subdomains of) the intra- and/or interpersonal domain (i.e., interventions primarily aiming to improve students’ physical health (e.g., prevention of substance use, nutrition, pregnancy, STDs) or prevent mental disorders (e.g., depression) were excluded.), (4) the intervention was universal, so targeting all students, (5) the participants were inmiddle school or high school (Grades 6 – 12), (6) the study included a control group, (7) the study included a quantitative baseline and post intervention measurement of (subdomains of) the intrapersonal domain and/or interpersonal domain, (8) sufficient information concerning baseline and post intervention measurements was reported, or obtained after contact with the author, so that effect sizes could be calculated post intervention, corrected for baseline differences, (9) the study was written in English, and (10) the study was published as article, book, or book chapter. Research has shown that including unpublished studies does not reduce the possible impact of publication bias and is sometimes even counterproductive due to selection bias (Ferguson & Brannick, 2012). Literature Search We searched four databases (i.e., PsycINFO, PubMed, ERIC, and CENTRAL). Search terms were used to elicit school-based interventions (e.g., school, class), interventions (e.g., prevention, intervention), adolescents (e.g., adolescent, youth), and intra- and interpersonal outcomes (e.g., self-esteem, social competence). Because these search terms led to an extremely high number of studies, we added some restrictions to the search, to avoid picking up interventions targeting other populations (e.g., preschool, clinical) or domains (e.g., substance use, lifestyle) than targeted in this study. This search (April 2019) resulted in 6,102 studies in PsycINFO, 2,964 studies in PubMed, 1,683 studies in ERIC, and 567 studies in CENTRAL. Removal of duplicates resulted in 9,498 unique studies. In addition, reference lists of included studies and identified relevant reviews and meta-analyses were searched. This resulted in 22 additional studies. All studies identified by the search were first screened for eligibility based on their title and abstract. Based on this screening 9,068 studies (95%) were excluded. 6