Maartje Boer

CHAPTER 7 218 throughout this period. Second, problematic SMU manifests in different ways, depending on the risk profile: While problematic SMU of adolescents with low self-control seems externally visible through high SMU frequency, problematic SMU of adolescents with low social competencies may be more internally present, given that they do not show high SMU frequency. This finding suggests that for this latter group, problematic SMU may be more difficult to detect for professionals and parents that are concerned with the wellbeing of young adolescents. In addition, we did not observe a variable trajectory that captured the onset of problematic SMU, which implies that problematic SMUmay emerge more at the start of early adolescence. Correspondingly, research shows that 11-year-olds may already endorse multiple problematic SMU criteria (Stevens et al., 2018). Other research among Dutch children shows that in 2017, the percentage of 10-year-olds that used Whatsapp, Snapchat, and Instagram was 69%, 25%, and 19%, respectively. Among 11-year-olds, this was 82%, 30%, and 35%, respectively (Kennisnet, 2017). Given that the majority of the 10- and 11-year-olds use social media and that they may already experience problematic SMU in this period, it is important that parents and teachers monitor and support children around this age who experience severe problems in regulating their use or whose use goes at the expense of activities important to children’s health. This study showed that lower subjective wellbeing and self-control predicted problematic SMU, although this was not found in previous research using the same data (Boer, Stevens, et al., 2020; Boer, Stevens, Finkenauer, De Looze, et al., 2021). It should be noted, however, that previous research focused on within-person processes and showed that adolescents with lower levels of subjective wellbeing or self-control relative to their individual average did not show an increase in problematic SMU . The present study focused on between-person comparisons and showed that adolescents with lower levels of subjective wellbeing and self-control relative to other adolescents were likely to report persistent and variable high levels of problematic SMU . Together, this suggests that particularly the between-person (i.e., trait- like) differences in wellbeing and self-control may determine adolescents’ vulnerability to problematic SMU.