Maartje Boer

SMU AND MENTAL HEALTH 163 6 ‘Feeling hopeless about the future’, ‘Feeling nervous or tense’, and ‘Worrying too much about things’ (1 never to 5 always ). The scale has been validated among U.S. secondary school students but has been adopted extensively in adolescent surveys (Compas et al., 1993), also in translated form among Dutch adolescents (Engels et al., 2001; Van Rooij et al., 2014). The scale has been found to have appropriate internal consistency and test-retest reliability (Compas et al., 1993). In the present sample, Cronbach’s alpha varied between 0.81 and 0.87 in all waves. Life Satisfaction Respondents indicated their life satisfaction using the 7-item Student’s Life Satisfaction Scale (Huebner, 1991). Respondents were asked about their thoughts around their own life: ‘My life is going well’, ‘My life is just right’, ‘I would like to change many things in my life’, ‘I wish I had a different kind of life’, ‘I have a good life’, ‘I have what I want in life’, and ‘My life is better than most kids’ (1 strongly disagree to 6 strongly agree ). The third and fourth item were recoded such that higher values indicated higher life satisfaction. The scale has been validated extensively among elementary and secondary school U.S. students and showed adequate convergent and discriminant validity and test-retest reliability (Huebner, 2004). The scale has been translated and adopted across many countries (Proctor et al., 2009). In the present study, Cronbach’s alpha varied between 0.83 and 0.84 in all waves. Upward Social Comparisons A newly developed 5-item scale measured the extent to which respondents engage in upward social comparison during their SMU. This scale was developed because existing validated measures on social comparison typically assess respondents’ overall tendency to compare themselves to others (i.e., not specifically as a result of viewing social media). Respondents indicated, when viewing their peers’ messages, photos, or movies on social network sites, how often they thought ‘He or she does more fun things than I do’, ‘He or she has more friends than I do’, ‘He or she is more popular dan me’, ‘He or she received more ‘likes’ than me’, and ‘He or she looks better than I do’ (1 never to 5 very often ) . Cronbach’s alpha was 0.88 in all three waves.