Maartje Boer

CHAPTER 4 116 higher life satisfaction than non-intense users, whereas in countries with a lower than average prevalence, intense users reported lower life satisfaction than non-intense users ( B = 1.229, p < 0.001; Figure 4.2B). This cross-level interaction explained 80.0% of the country-variance in this association. Adding the country-level prevalence of problematic SMU as additional cross- level interaction did not improve model fit (Table 4.2, M1 e ). Intense users reported more frequent psychological complaints than non-intense users ( B = 0.110, p < 0.001), although this was not observed in all countries (95% PI = -0.030 to 0.248). The higher the country-level prevalence of intense SMU, the smaller the difference in psychological complaints between intense and non-intense users, with no differences observed in the highest prevalence countries ( B = -0.533, p = 0.002; Figure 4.2B). Although this cross- level interaction only improved AIC, but not BIC (Table 4.2, M2 d ), it explained 40.0% of the country-variance in this association. Adding the country-level prevalence of problematic SMU as additional cross-level interaction did not improve model fit (Table 4.2, M2 e ). School Wellbeing On average, intense SMU was negatively associated with school satisfaction ( B = -0.064, p < 0.001) and positively with school pressure ( B = 0.055, p < 0.001), although these associations were close to zero. In some countries, the negative association with school satisfaction and the positive association with school pressure were stronger (95%PIs = -0.152 to 0.024 and -0.033 to 0.143, respectively). These country-variances were not related to the country-level prevalence of intense and problematic SMU, because models including these cross-level interactions did not show better model fit (Table 4.2, M3 d,e and M4 d,e ). Social Wellbeing Intense and non-intense users reported about similar levels of family support on average ( B = 0.039, p = 0.016). However, there was variation in this association, with intense SMU being positively related to family support in some countries and negatively related in other countries (95% PI = -0.145 to 0.227). In countries with a high prevalence of intense SMU, intense users reported more family support than non-intense users, while in countries with a low prevalence, intense users reported less family support than non-intense users ( B = 0.816, p