Maartje Boer

CHAPTER 3 58 Abstract There is currently no cross-national validation of a scale that measures problematic social media use (SMU). The present study investigated and compared the psychometric properties of the Social Media Disorder (SMD)- scale among young adolescents. Data came from 222,532 adolescents from 44 countries participating in the Health Behaviour in School-aged Children (HBSC) survey (2017/2018). The HBSC survey was conducted in the European region and Canada. Participants were on average 13.5 years old ( SD = 1.6) and 51.2% were girls. Problematic SMU was measured using the 9-item SMD- scale with dichotomous response options. Confirmatory factor analyses (CFA) showed good model fit for a one-factor model across all countries (min. comparative fit index (CFI) and Tucker–Lewis index (TLI): 0.963 and 0.951, max. root mean square error of approximation (RMSEA) and standardized root mean square residual (SRMR): 0.057 and 0.060), confirming structural validity. The internal consistency of the items was adequate in all countries (min. alpha = 0.840), indicating that the scale provides reliable scores. Multigroup CFA showed that the factor structure was measurement invariant across countries ( Δ CFI = -0.010, Δ RMSEA = 0.003), suggesting that adolescents’ level of problematic SMU can be reliably compared cross-nationally. In all countries, gender and socioeconomic invariance was established, and age invariance was found in 43 out of 44 countries. In line with prior research, in almost all countries, problematic SMU related to poorer mental wellbeing (range β STDY = 0.193 to 0.924, p < 0.05) and higher intensity of online communication (range β STDY = 0.163 to 0.635, p < 0.05), confirming appropriate criterion validity. The SMD-scale appears to be suitable for measuring and comparing problematic social media use among young adolescents across many national contexts. Keywords : Problematic social media use, social media addiction, international validation, psychometric tests, adolescents, HBSC.