The Digital Detox study is designed as a randomized controlled trial (two unblinded parallel groups) to examine the effects of reducing smartphone screentime on mental health. After giving informed consent, participants will be screened for eligibility. Inclusion criteria are adult subjects (greater-equal 18 years) using their smartphone daily for 3 hours or more, with sufficient German skills and no ongoing psychotherapy, psychological or psychopharmacological treatment. For eligibility screening, participants have to upload a screenshot of their smartphone screen time of the last week, have to state about mental health disorders (self-report) and their sociodemographic variables (age, gender, country of residence, education and professional status, urban/rural nature of place of residence), and have to fill out the following questionnaires: depressive symptoms (PHQ-9), well-being (WHO-5), sleep quality (ISI), stress (PSQ-20), loneliness (three-item loneliness scale), physical activity, and smartphone usage behavior.
If the inclusion criteria are met, participants will be randomized to the intervention or control group. The intervention consists of a three-week screen time reduction to a maximum of 2 hours per day for 3 consecutive weeks. The control group continues to use their smartphones as usual during this time. At the beginning of the study (=baseline T0), all participants will complete the following primary outcome measures (depressive symptoms (PHQ-9), well-being (WHO-5), sleep quality (ISI), stress (PSQ-20)) and secondary outcome measures (loneliness (three-item loneliness scale), craving (CEQ-F), physical activity). Both groups will also complete items on loneliness and physical activity twice during the intervention (after the first and second week of the intervention) to monitor changes in these variables during the intervention. After the three weeks of intervention (post-intervention T1), both groups will again fill out the the same outcome measures as for T0. After the 3-week intervention, there are no further restrictions regarding the participants' smartphone screen time. Follow-up (T2) will be after 3 more weeks and the same outcome measures as for T0 and T1 will be collected.
The weekly smartphone screen time is assessed via self-reporting and screenshot upload. Information is also provided on the weekly activations of the smartphone and a screenshot is uploaded of the most frequently used apps. All data is collected weekly for the previous week.
The study will be performed entirely via a smartphone app (ESMIra), which is designed especially to run longitudinal studies.
Primary hypotheses:
* H1: Reducing smartphone use to a maximum of 2 hours/day over 3 weeks leads to a difference in the depressive symptoms of the intervention participants before and after participating in the intervention.
* H2: Reducing smartphone use to a maximum of 2 hours/day over 3 weeks leads to a difference in the the sleep quality of the intervention participants before and after participating in the intervention.
* H3: Reducing smartphone use to a maximum of 2 hours/day over 3 weeks leads to a difference in perceived stress of the intervention participants before and after participating in the intervention.
* H4: Reducing smartphone use to a maximum of 2 hours/day over 3 weeks leads to a difference in the well-being of the intervention participants before and after participating in the intervention.
* H5: The reduction in smartphone use to a maximum of 2 hours/day over 3 weeks led to a difference in depressive symptoms between the control and intervention groups at the post-intervention time point.
* H6: The reduction in smartphone use to a maximum of 2 hours/day over 3 weeks led to a difference in sleep quality between the control and intervention groups at the post-intervention time point.
* H7: The reduction in smartphone use to a maximum of 2 hours/day over 3 weeks led to a difference in perceived stress between the control and intervention groups at the post-intervention time point.
* H8: The reduction in smartphone use to a maximum of 2 hours/day over 3 weeks led to a difference in well-being between the control and intervention groups at the post-intervention time point.