Maartje Boer

SMU AND MENTAL HEALTH 181 6 Strengths and Limitations The present study has important strengths, such as the conceptual difference between SMU intensity and SMU problems in relation with mental health, the definition of mental health that encompasses the presence of wellbeing as well as absence of mental illnesses, the longitudinal data and innovative modelling techniques that provide insight into the directionality of associations, and the number of mediators investigated that allow for a more in-depth understanding of associations. However, findings of this study should be interpreted in light of several limitations. First, our conceptualization of SMU intensity combines passive (e.g., viewing social media) and active social media activities (e.g., responding to messages). Disentangling the independent effects of passive and active SMU intensity was beyond the scope of the present study. Our findings should be interpreted in light of this operationalization: When examining overall SMU intensity, SMU intensity and mental health do not seem to be associated over time. However, it has been proposed that particularly passive SMU threatens mental health (Odgers & Jensen, 2020; Orben, 2020a), although experimental and longitudinal research suggests that this depends on the characteristics of the adolescent (Beyens, Pouwels, Valkenburg, et al., 2020; De Vries et al., 2018; Wenninger et al., 2014). To consolidate our conclusion that SMU intensity does not impair mental health, more research testing the effects of passive and active SMU intensity separately is essential. To that end, the use of objective measures, such as tracked time spent or frequency of active and passive SMU, would be promising, as such measures provide more reliable estimates of SMU than self-report measures (Junco, 2013). Second, we proposed thatmental health problems could both cause and result from SMU problems. However, it could be argued that this proposition reflects a circular relationship between mental health and SMU problems rather than a bidirectional association. Mental health problems that cause SMU problems may differ frommental health problems that arise from SMU problems. More specifically, while it is argued that pre-existing pathological mental health problems underly the development of SMU problems (Davis, 2001; Griffiths, 2013), SMU problems may not lead to pathological levels of mental health problems, but rather to decreases in mental health in general. Third, although the yearly time intervals of the repeated measures provide