Maartje Boer

CROSS-NATIONAL VALIDATION OF THE SMD-SCALE 75 3 and adolescents with low, middle, and high socioeconomic status. Therefore, researchers can use the scale to accurately identify which of these subgroups are at risk of problematic SMU, which is considered important given the possible detrimental consequences of problematic SMU (Boer, Stevens, et al., 2020; Boer, Stevens, Finkenauer, De Looze, et al., 2021). The observed pooled effect sizes from the criterion validity analysis were in line with the literature (Frost & Rickwood, 2017; Huang, 2020; Marino et al., 2018b; Parry et al., 2020). Problematic SMU was more strongly associated with psychosomatic complaints than with low life satisfaction, which parallels review studies showing a stronger relationship between problematic SMU and indicators of negative mental wellbeing (e.g., depression) compared with indicators of positive mental wellbeing (e.g., self-esteem) (Huang, 2020; Marino et al., 2018b). Not only do these findings confirm that the scores on the scale are related to constructs they should theoretically be related to; they also highlight that, worldwide, problematic users face several similar mental health risks. If these associations occur because problematic SMU leads to significant psychological harm, as suggested by some longitudinal studies (Boer, Stevens, Finkenauer, De Looze, et al., 2021; Raudsepp, 2019), then problematic SMUmay reflect addiction-like behavior, which has been questioned (Kardefelt-Winther etal., 2017).However, toverify this,moreresearch is required, particularly focusing on whether problematic SMU impairs mental health and other aspects of daily life, assessed in clinical settings. Furthermore, the finding that problematic SMU is a global risk factor for adolescents’ mental wellbeing emphasizes the relevance for the development of prevention and intervention programs on (reducing) problematic SMU, for example by supporting adolescents in regulating their SMU. In addition, the observed small to moderate effect size of the (positive) association between problematic SMU and online communication intensity may be regarded as counterintuitive (Frost & Rickwood, 2017). However, this effect size is in line with earlier meta-analytic findings on the relationship between problematic SMU and the intensity of (tracked) SMU activities (Frost & Rickwood, 2017; Parry et al., 2020), which supports the suggestion that the intensity of SMUactivities andproblematic SMU shouldbe regarded as related but different dimensions of SMU (Boer, Stevens, Finkenauer, De Looze, et al., 2021; Boer, Van den Eijnden, et al., 2020; Parry et al., 2020). Although many