Esther Mertens

74 | Chapter 4 stimulate adolescents’ competencies and prevent the development of problems in the intrapersonal (i.e., psychological wellbeing, resilience, sexual autonomy, and internalizing behavior) and interpersonal domain (i.e., interpersonal relations in the class, externalizing behavior, aggression, bullying, and victimization). We hypothesized that more vulnerable adolescents – based on their levels of personality traits, i.e., low levels of Extraversion, Agreeableness, or Conscientiousness, or high levels of Neuroticism – benefit more from the intervention than less vulnerable adolescents. Furthermore, we hypothesized that adolescents who can effectively transfer skills learned during an intervention to their daily lives benefit more from the intervention (e.g., high levels of Conscientiousness or Openness to experiences). Method Procedure and Design We examined the effectiveness of R&W by means of a randomized controlled trial with three intervention conditions and one control condition. The intervention was examined in three different conditions as part of a larger project. One of the aims of this project was to examine whether the width of the intervention’s ecological focus (i.e., the extent to which multiple systems are involved in the intervention) affected intervention effects. These different intervention conditions were not presumed to influence the moderating effect of personality. In the ‘Light’ condition, only a core team of teachers was involved in the intervention. In the ‘Standard’ condition, the entire teaching staff was involved. In the ‘Plus’ condition, the entire teaching staff and parents were involved. In the Control condition, current school policy to improve students’ competencies and prevent problems in the intra- and interpersonal domain was implemented (i.e., care as usual). Interested schools were screened for eligibility by the researchers. Special education schools and schools that had implemented R&W in the last two years were excluded. Thirteen schools in urban and rural areas in the Netherlands were included. An online number generator was used to randomize the schools to a condition stratified by school size (< 100 students in 7 th Grade, > 100 students in 7 th Grade) to enhance an equal distribution of adolescents. After randomization and before data collection started, one control school dropped out due to changed school management and was replaced by another school (see Figure 1 for the flow chart).