PeerScreen Trial - Reducing Screen Media Use in Peer-groups of Young People

The PeerScreen trial is a parallel-group cluster-randomized controlled trial in which peer groups of adolescents and young adults aged 13-24 years are randomized to either a four-week screen media reduction intervention or a control condition. Random allocation of each peer group will occur after completion of a 14-day baseline assessment protocol. Randomization will be conducted using computer-generated block randomization (block sizes 2-6), stratified by mean peer group age (\<18 vs. ≥18 years). In practice, a researcher will log in to an online platform and click "randomize," thereby ensuring allocation concealment. Participants in the intervention group will be instructed to reduce smartphone use to one hour per day, limit television, computer, and tablet use to 14 hours per week, and keep screen media devices outside the bedroom. The target sample is 80 peer groups (2-6 peers per group) of adolescents (13-17 years) and young adults (18-24 years), to be recruited via a separate survey study. This survey will be conducted in classes across secondary and higher educational institutions (e.g., secondary schools, high schools, vocational schools, university colleges, and universities) and will describe screen media behaviors among Danish youth. Before administration of the survey, the research team will introduce the PeerScreen trial in each class. At the end of the survey, students will be asked whether they are interested in participating in an experimental study and whether the research team may contact them for follow-up. Written information about the experiment will be provided to interested students during classroom visits and distributed via the school and its online platforms, along with a registration link, after the visits. This procedure will allow students to express interest at a later stage if preferred. Data collection will combine questionnaires on mental health and well-being, daily reports of mood, sleepiness, and social interactions, and objective monitoring of screen media use, sleep, physical activity, and heart rate variability using a custom application and a wearable device. Bluetooth beacon data will be used to assess social interactions objectively, and geolocation data will be used to provide contextual information about these interactions.