Maartje Boer

CHAPTER 4 120 Discussion Using data from 29 countries, the present study showed that adolescents’ intense SMU was positively or negatively associated with their wellbeing, dependent on the wellbeing domain and national context, whereas problematic SMU was indicative of low wellbeing on all investigated domains and in all countries. More specifically, in countries with a low prevalence of intense SMU, intense users reportedmore frequent psychological complaints, lower life satisfaction, and lower levels of family support. However, in countries withahigh intense SMUprevalence, intense SMUwasweakly or not associated with psychological complaints, and was positively related to family support and life satisfaction. Only in some countries, intense users reported lower school satisfaction and higher school pressure than non-intense users, but this did not depend on the country-level prevalence rates of either intense or problematic SMU. Intense SMU was related to higher levels of friends support across all countries, and this association became stronger as country-level prevalence of intense SMU increased. Findings for problematic SMU were much more consistent than for intense SMU, with lower levels of mental, school, and social wellbeing among problematic users in all countries, although there was country-variance in the strength of these associations. This variance could not be explained by the country-level prevalence of intense and problematic SMU, except for the negative associationbetweenproblematic SMUand social wellbeing (i.e., family support and friend support), which was stronger in countries with a lower prevalence of problematic SMU. In addition, although countries’ prevalence rates of intense and problematic SMU differed substantially, these differences were not explained by the countries’ mobile internet accessibility. By highlighting that the relationship between intense SMU and adolescent wellbeing depends on the wellbeing indicator and the national context, our results challenge the notion that intense SMU is related to lower wellbeing (Primack & Escobar-Viera, 2017; Twenge, Joiner, et al., 2018; Underwood & Ehrenreich, 2017). Our results support findings from systematic reviews showing that SMU can be positively and negatively associated with wellbeing (Best et al., 2014; Verduyn et al., 2017). In fact, given that in countries with high levels of intense SMU intense users reported higher life satisfaction and higher levels of family support than non-intense users, and that in all