Maartje Boer

SUMMARY AND DISCUSSION 301 9 models imply that SMU problems predicted subsequent lower mental health, regardless of adolescents’ stable level of mental health. This means that SMU problems may exacerbate pre-existing psychological vulnerabilities, but also pose a risk to the mental health of adolescents who do not show such vulnerabilities. Next, the finding that the association between SMU intensity and wellbeing depended on individual as well as country factors (Key finding 6; Chapters 4, 8) supports the differential susceptibility to media effects model (Valkenburg & Peter, 2013). This theoretical model posits that media effects are contingent on dispositional factors, such as gender, personality, andmoral values, as well as social factors that are context-related, such as the cultural norms and habits within a society (Valkenburg & Peter, 2013). According to our findings, a social factor that influenced the association between SMU intensity and wellbeing was the extent to which intense SMU was the norm within the adolescent population. Applying the normalization thesis , this may be because once risk behaviors become normalized within the adolescent population, these behaviors may represent adolescents without problematic profiles, or even well-adjusted adolescents (Haskuka et al., 2018; Pennay & Measham, 2016; Sznitman et al., 2015). As such, when high SMU intensity is normalized among adolescents within the society, intense users may represent mainstream adolescents, whereas in societies where high SMU intensity is rather exceptional, intense users may be more vulnerable adolescents. Other research also found that the association between SMU intensity and wellbeing depended on the social context (O’Leary & Volkmer, 2021). A theoretical suggestion that was not supported by our findings was the active versus passive SMU hypothesis (Chapter 8). According to this suggestion, active SMU, which involves sharing content and communication with others on social media, increases one’s social capital and sense of belonging, thereby enhancing wellbeing. In contrast, passive SMU, which refers to viewing other people’s messages or photos on social media that are typically biased toward positivity, induces feelings of envy, in turn, decreasing wellbeing (Dienlin & Johannes, 2020; Verduyn et al., 2017). Recent experience sampling studies also failed to find support for this hypothesis (Beyens, Pouwels, Van Driel, et al., 2020; Jensen et al., 2019; Valkenburg, Beyens, et al.,