Maartje Boer

CHAPTER 1 14 problematic SMU are negatively related to wellbeing. As a result, it is unknown which SMU behavior induces negative associations with wellbeing. More specifically, it is unclearwhether engaging inhighSMU intensity is detrimental to wellbeing, as some studies have suggested (e.g., Kelly et al., 2018; Twenge et al., 2018), or whether these associations were spurious because they could be explained by problematic SMU. Given that nowadays many adolescents use social media intensively (Anderson & Jiang, 2018; Smahel et al., 2020), and the widespread concerns about the overuse of social media to adolescents’ health (Orben, 2020b; Unicef, 2017), it is crucial to identify which type of SMU behavior induces potential harmful effects. Possibly, adolescents engaging in high SMU intensity may be well able to combine their SMU with a healthy lifestyle, because high SMU intensity does not necessarily indicate any loss of control over SMU or interference with activities that are relevant to adolescent wellbeing, such as face-to- face contact with peers. Instead, high SMU intensity may be understood as a common adolescent behavior that is relevant to their individual development during adolescence. Detrimental consequences may rather emerge when adolescents’ SMU is problematic, because in that case, adolescents have lost control over their SMU behavior. Put differently, adolescents who are using social media problematically have a decreased ability to regulate SMU impulses and constantly think about SMU (Griffiths, 2013; Griffiths et al., 2014). Such loss of agency over thoughts, emotions, and behaviors, may interfere with adolescents’ daily lives and as such, be a source of decreased wellbeing. Thereby, problematic SMU may be more harmful to wellbeing than high levels of SMU intensity. To our knowledge, only two prior studies have disentangled the effects of adolescents’ intensity of SMU and problematic SMU. Based on longitudinal data that were also used in chapters included in this dissertation, Van den Eijnden and colleagues (2018) showed that SMU problems, but not SMU intensity, predicted lower levels of life satisfaction over time. In line with these findings, a cross-sectional study among U.S. young adults (aged 19 to 32) revealed that problematic SMU, but not the intensity if SMU, was associated with more depressive symptoms (Shensa et al., 2017). These studies provide important first insights into the differences between the intensity of SMU and problematic SMU, in particular in their differential associations with wellbeing. However, additional knowledge gaps related to SMU intensity,