Maartje Boer

THE COMPLEX ASSOCIATION BETWEEN SMU AND WELLBEING 239 8 In another longitudinal study, overall SMU intensity was positively related to depression and negatively to self-esteem, both at the between-person and within-person level, but effect sizes were not reported (Boers et al., 2019). Thus, most studies that separate within-person from between-person variance show no or a negligible negative association at the within-person level, while the association at the between-person level is more inconsistent. Current Study Findings on the association between SMU intensity and wellbeing are conflicting. Based on the existing literature, we identified five theoretical and methodological factors that may explain these inconsistencies. Translating these factors into research questions (RQs), the present study investigated: • RQ1: Which type of SMU activity is negatively associated with adolescent wellbeing? • RQ2: Is the association between SMU intensity and wellbeing non-linear? • RQ3: (a) Does the association between SMU intensity and wellbeing differ across adolescents and if so, (b) can these differences be explained by adolescents’ tendency to engage in upward social comparisons? • RQ4: Is the negative association between SMU intensity and wellbeing confounded by SMU problems? • RQ5: Does the negative association between SMU intensity andwellbeing occur at the within-person and/or between-person level? These research questions have mostly been examined in isolation. Therefore, it remains unknown whether and how they affect the association between SMU intensity and wellbeing when being considered in concert. This is important to improve our understanding of possible SMU effects on adolescent wellbeing and to fuel specific directions for future research. To study our research questions, we used four waves of longitudinal data with yearly time intervals among Dutch secondary school adolescents ( n = 1,419). We examined adolescents’ SMU intensity using self-reported SMU frequencies and wellbeing using self-reported life satisfaction. While the scientific discourse on SMU effects often focuses on a dichotomy between active and passive SMU activities, the present study distinguished six SMU activities that ranged from more active (e.g., posting messages on SNS) to more passive (e.g., viewing messages on SNS).