Maartje Boer

SUMMARY AND DISCUSSION 305 9 based on strengthening motivation to change, self-efficacy (Michie et al., 2011) and implementation intentions (Gollwitzer & Sheeran, 2006) may also be helpful. For example, preliminary findings on the effectiveness of an intervention aimed at raising awareness and enhancing control over smartphone use among Dutch university students showed that students’ level of problematic smartphone use was reduced when they had formulated implementation intentions to use their smartphone more consciously (e.g., leave the smartphone outside of the bedroom to resist temptation to use the smartphone in bed) (Schiltkamp, 2021). We stress that some adolescents may display SMU problems because of, for example, poor mental health (Key finding 4; Chapter 7). These adolescents may be more sensitive to SMU problems, because SMU possibly relieves their sorrows or calms their restless thoughts, in other words, SMU may help them to escape fromor to copewith their problems (Davis, 2001; Kuss &Griffiths, 2011, 2017). As such, SMU problems may be a symptom of underlying vulnerability. Therefore, problematic users may benefit from individual support from, for example, a (school) counsellor or psychologist, who addresses the source of their problematic attachment to SMU. Future Directions Alongside the abovementioned implications, this dissertation opens avenues for several new research directions. We divided these directions into four categories, which we outline below. Extending Knowledge on the Clinical Relevance of Problematic SMU In the past few years, many scholars have questioned whether problematic SMU is clinically relevant (Brand et al., 2020; Kardefelt-Winther et al., 2017; Starcevic et al., 2018). To answer this, it should be determined whether the behavior constitutes a behavioral addiction. Although our findings suggest that problematic SMU, as measured by the SMD-scale, represents addiction- like behavior, above we stressed that more research on the development and consequences of SMU problems throughout different developmental periods is essential to consolidate this suggestion. Furthermore, data other than self-