Digital Detox Study: A Randomized Controlled Trial

The aim of the present RCT is to investigate the effect of smartphone screen time reduction on mental health indicators in healthy, 18-29 yo Austrian students.

After inclusion and randomization to intervention- and control group, normal screen time behavior will be assessed for 10-days. After that, the mental health parameters will be carried out in both groups as a baseline survey (T0). After that, intervention group should limit smartphone screen time to less than 2 hours per day for three consecutive weeks. Control group should use smartphones as usual. After that, mental health parameters will be assessed again in both groups (post-intervention, T1). After T1, there are no further requirements regarding screen time. Mental health parameters will be assessed again in both groups at follow-up (T2).

Main outcome parameters are 1) Well-Being (WHO-5), depressive symptoms (PHQ-9), stress (PSQ-20), and sleep quality (ISI).

The primary hypothesis (stated at Open Science Framework before Enrollment: https://osf.io/a9k76) is that mental health indicators, particularly stress, depressive symptoms, and sleep quality will improve throughout the intervention compared to the control group as well as to baseline.

According to the power-analysis (small to medium effect size of d=.45, power .8, significance level \< .05, icc = .05), a sample of N \> 100 should be recruited through newsletter, notices and social media. The inclusion criteria are more than 3 hours of screen time per day, no mental disorder, no ongoing psychotherapy or use of psychotropic drugs.

After signing the informed consent, participants have to download an App (ESMira®), which processes the whole study. The first step is to fill out sociodemographic data, smartphone use and mental health questionnaires. After controlling for inclusion- and exclusion criteria, ESMira will randomize into intervention- (IG) and control group (CG). Participants in the control group (CG) should continue their smartphone behavior unchanged throughout the entire study period. Participants in the intervention group (IG) should continue their smartphone usage unchanged for the first 10 days (Baseline.) After that, the mental health parameters will be carried out in both groups as a baseline survey (T0). After that, participants of the intervention group should limit their smartphone screen time under two hours per day for three weeks. To comply with that, participants should use the limiter function of their smartphone or download an additional app. A screen shot of the screen time has to be uploaded weekly on Monday for the previous week (Monday to Sunday). At the end of the intervention (t1), the mental health questionnaires will be collected again in both groups. After T1, there are no further requirements regarding screen time. Mental health parameters will be assessed again in both groups at follow-up (T2).

During the study period participants will be asked to additionally wear a fitness tracker to measure daily movement as well as objective stress parameters.

Data collection and randomization The whole data collection procedure will be carried out through the ESMira App. ESMira is a tool for running longitudinal studies (ESM, AA, EMA, ...) with completely anonymized communication with participants and data collection.

Smartphone screen time Weekly screen time will be documented in both groups using the smartphones' built-in screen time measurements.

Statistical plan

Repeated measurements ANOVAs (rm-ANOVA) will be applied to analyze differences. Difference between t0 (baseline) and t1 (post-intervention) in the intervention group and on the difference between control group and intervention group are the primary hypotheses. Effects (between- as well as within group) will be analyzed for all 3 measurement points as well. Furthermore, a secondary analysis will be applied to analyze the sub-sample that strictly adhered to the time limits.

In case of baseline group-differences, variables will be added as covariates in the rm-ANOVA. A Greenhouse-Geisser correction will be applied, if sphericity assumption is violated. In the post hoc tests, Bonferroni correction will be applied to adjust for multiple comparisons.

Missing values will be dealt with via maximum likelihood estimation. Percentage changes in the main outcomes between baseline and post-intervention will be calculated.

Eligibility Criteria:
Inclusion Criteria:

* 18-29 years old
* male/female
* daily screen time \> 3 h/d
* no mental disorder
* no ongoing psychotherapy
* no psychotropic drugs

Exclusion Criteria:

* \< 18 yo or \> 29 yo
* daily screen time \< 3 h/d
* mental disorder (self-statement)
* in ongoing psychotherapy
* psychotropic drug use