Effects of Reducing Screen Media Use on Mental Health, Sleep, Physical Activity, Heart Rate Variability, and Behavioral Patterns in Peer-groups of Young People: A Study Protocol for a Cluster-randomized Controlled Trial

Inclusion Criteria

Inclusion Criteria: * Participants must have at least 2 hours/day of self-reported smartphone use during leisure time (data from the survey study) * Members of each participant's household must be willing to support the participant in adhering to the prescribed intervention (data from recruitment interview) * Participants must have enough discretionary leisure time for possible in-person activities on a weekly basis throughout the study period (verified at the information meeting) Exclusion Criteria: * Participants with no smartphone will be excluded (data from recruitment interview) * Participants with no social media profiles will be excluded (data from recruitment interview) * Participants who currently participate in other experimental studies will be excluded (data from recruitment interview) * Participants who have been hospitalized or prescribed sick leave within the past 3 months due to a mental illness will be excluded (data from recruitment interview)