Maartje Boer

SMU AND WELLBEING ACROSS COUNTRIES 105 4 Measham, 2016), these behaviors may become normalized and consequently represent mainstream adolescents without problematic profiles (Sznitman et al., 2015). Hence, engaging in these behaviors may not necessarily indicate lower wellbeing. Similarly, when intense andproblematic SMUarewidespread in society, these behaviors may become normalized. Consequently, when the country-level prevalence of intense or problematic SMU is high, the proposed negative associations with wellbeing may be low or even absent. In addition, differences in the country-level prevalence of intense and problematic SMU may be related to cross-national differences in the accessibility of mobile internet, such as the countries’ average costs and speed of mobile internet, as adolescents typically use social media through mobile internet devices, such as smartphones (Eurostat, 2015). Current Study Using data from 29 countries participating in the Health Behaviour in School- aged Children (HBSC) survey (2017/2018), the present study investigated whether adolescents’ intense and problematic SMU were associated with their wellbeing, and whether these associations varied across countries. We expected that, compared with intense SMU, problematic SMU would be more strongly associated with lower mental, school, and social wellbeing. We also expected that associations between both types of SMU and low wellbeing would be weaker in countries with a higher prevalence of intense and problematic SMU. The study also investigated whether cross-national differences in the prevalence of intense and problematic SMU were related to country-level mobile internet access. We expected that countries with more favourable mobile internet access would report a higher prevalence of adolescent intense and problematic SMU. Methods Sample The HBSC survey is a cross-national study that has been conducted every four years since 1983 to monitor the health behavior of 11-, 13-, and 15-year- olds across Europe, North America, and the Middle East. The present study used the 2017/2018 data, which included nationally representative data of