Background: The decline of adolescents’ mental well-being, coinciding with an increase of social media as a primary platform for adolescents’ social life, have been suggested to be associated. The current study aimed to investigate the association between social media frequency, problematic social media use (PSMU), and adolescents’ life satisfaction, the potential moderating effect of physical activity on these associations, and in-group differences in the associations by gender and grade. Method: The sample consisted of cross-sectional, self-reported, data from the Swedish cohort of the 2017/18 Health Behaviour in School-aged Children (HBSC) study (n=3,446). Ordinal logistic regression was used to estimate the odds ratios for the association between the outcome variable, low life satisfaction, and the exposure variables: Social media frequency, measured in time spent on communication through social media, and PSMU, measured as the number of symptoms from the Social Media Disorder scale, while adjusting for covariates. Gender and grade stratified analysis was conducted, as well as interaction analysis of physical activity. Results: After adjustment for covariates, no association was found between high social media frequency use and life satisfaction, but a small association with was found among adolescents with lower social media frequency. There was a significant and graded association between PSMU and lower life satisfaction. Stratified analysis showed gender and age differences in the associations, with higher odds of lower life satisfaction for girls and 13- and 15-year-olds. No moderating effect of physical activity was found for any of the associations. Conclusion: Social media use can be considered a proximal social determinant of adolescent health through its demonstrated association with life satisfaction. PSMU, as well as girls and older adolescents, has a stronger connection to lower life satisfaction than frequency of use and should be considered in policy work for prevention and improvement of adolescent health.

Social media has become ubiquitous in modern society. Both as a way to connect with others and as a popular form of entertainment and relaxation. This dependency on social media can lead both to beneficial and adverse consequences. A common concern about social media use relates to how active or passive a user is, with some indicating that passive behaviours, such as absently scrolling through the feed are particularly harmful. Research that investigates social media’s adverse effect on the individual depending on the user’s engagement level currently suffers from problems with categorisation, methodology and philosophy. This thesis sought to fill this research gap. Its research questions were accordingly: “What motivates adult users to use social media at various levels of engagement?” and “What factors of social media use impact adult users’ adverse emotional outcomes?”   To answer this research question, the study utilised a methodology of focus group discussion with pre-existing social groups consisting of adults aged 20-30, a demographic with potentially unique insight into their relationship with social media. This was followed by thematic analysis which in turn was placed within a framework of Use & gratification theory and the networked public. These theories were chosen since the research adheres to concepts of the active audience and disagrees with conceptualisations of the social media user as passive. Instead, low to high levels of engagement is used to describe individual behaviours. 4 main themes (Level of engagement, Problematic use, category of use and regulation) were discovered as well as 13 sub-themes.     The study discovered that individuals would use social media at several levels of engagement simultaneously but that behaviours could be assembled into four archetypes: Consumption (low level of engagement which included behaviours such as mindless scrolling), Lurking (low level of engagement which included both private and public browsing), socialisation (medium to high level of engagement which included communication), and production (high level of engagement which included publishing content). Different levels of engagement were associated with different adverse emotional outcomes which commonly occurred when users failed to effectively regulate their use or encountered harmful content. It was discovered that users encountered these issues largely due to the platform’s incentivisation through subtle and not so subtle means such as media design and notifications.