Intervention to reduce recreational screen-time in adolescents: Outcomes and mediators from the 'Switch-Off 4 Healthy Minds' (S4HM) cluster randomized controlled trial

Introduction. The primary objective was to evaluate the impact of the 'Switch-off 4 Healthy Minds' (S4HM) intervention on recreational screen-time in adolescents. Methods. Cluster randomized controlled trial with study measures at baseline and 6-months (post-intervention). Eligible participants reported exceeding recreational screen-time recommendations (i.e., >2 h/day). In total, 322 adolescents (mean age= 14.4 +/- 0.6 years) fromeight secondary schools in NewSouth Wales, Australiawere recruited. The S4HMinterventionwas guided by Self-Determination Theory and included: an interactive seminar, eHealth messaging, a behavioral contract and parental newsletters. The primary outcome was recreational screen-time. Secondary outcomes includedmental health (i. e., well-being, psychological distress, self-perceptions), objectively measured physical activity, and bodymass index (BMI). Outcome analyses were conducted using linear mixed models and mediation was examined using a product-of-coefficients test. Results. At post-intervention, significant reductions in screen-time were observed in both groups, with a greater reduction observed in the intervention group (-50 min/day versus -29 min, p < 0.05 for both). However, the adjusted difference in change between groups was not statistically significant (mean = -21.3 min/ day, p = 0.255). There were no significant intervention effects for mental health outcomes, physical activity or BMI. Significant mediation effects for autonomous motivation were found. Conclusions. Participants in both the S4HM intervention and control groups significantly reduced their screen-time, with no group-by-time effects. Enhancing autonomous motivation might be a useful intervention target for trials aimed at reducing adolescents' recreational screen-time. Trial registration. ACTRN12614000163606. (C) 2016 Elsevier Inc. All rights reserved.