Esther Mertens

| 89 Role Personality in School-Based Intervention parental report of personality instead of self-report. A limitation is the relatively low number of parent reports on adolescents’ personality. Missing data on parent reports were no issue when analyzing moderation with the interaction effects since missing data could be estimated in these models. However, these missing data could not be estimated in the multigroup models facilitating interpretation of the moderation effects. Furthermore, we ran 45 models with in total 135 interaction effects to examine moderation which could result in false positive results. We took this limitation into account by specifically focusing on moderation of intervention effects that showed a pattern across outcomes and conditions. It remains important that future research focuses more on the effects of personality traits on intervention effects and replicates our findings. In addition, it would be interesting to examine how combinations of personality traits influence intervention effects. For instance, future research could create a ‘risk index’ (e.g., Spoth et al., 2006) based on the number of present personality traits that make individuals more vulnerable to develop problems and study to what extent this risk index influences intervention effects. In conclusion, our study showed that personality traits are potentially relevant for intervention effects, especially in the intrapersonal domain, but more research is needed. In general, most intervention effects were not affected by personality traits. As a universal intervention aims to target all subgroups in the total population equally well, few moderation effects are to be expected (Nehmy & Wade, 2014) and subscribe the universal character of R&W. Nevertheless, three patterns of moderation by personality traits emerged. First, the intervention might be especially effective for adolescents vulnerable to develop problems – based on their levels of personality traits. Second, Extraversion might be an important moderator of intervention effects when the intervention requires sociability from participants. Third, personality traits seemmore important predictors and moderators in the intrapersonal domain than in the interpersonal domain. The present study highlights the importance of awareness that individuals can respond differently to interventions based on their levels of personality traits, especially in the intrapersonal domain. However, more research is needed concerning the role of personality traits in interventions’ effectiveness and how this moderation interacts with intervention characteristics before interventions can be optimally tailored. 4