Intervention to reduce recreational screen-time in adolescents: outcomes and mediators from the 'Switch-off 4 healthy minds' (S4HM) cluster randomized controlled trial

Introduction: Excessive recreational screen-time in adolescents is a public health problem in westernised countries, with little research conducted among adolescents. The primary objective of this study was to evaluate the impact of the ‘Switch-off 4 Healthy Minds’ (S4HM) intervention designed to reduce recreational screen-time in adolescents. Methods: A cluster randomized controlled trial with 6-month follow-up was conducted. Eight secondary schools in the Hunter region of New South Wales, Australia, were recruited. The S4HM intervention was guided by self-determination theory and included: an interactive seminar, eHealth messaging using social media, behavioral contract and parental newsletters. Participants (treatment n = 167, control n = 155) were adolescent males (34.5%) and females (65.5%) in grade 7 (Mean age = 14.4 ± 0.6 years), who reported exceeding recreational screen-time recommendations (i.e., > 2 h/day). The primary outcome was self-reported recreational screen-time measured at baseline and post-test (6-months). Secondary outcomes were mental health outcomes, objectively measured physical activity, and body mass index (BMI). Mediation analyses were conducted to determine if changes in motivation mediated the intervention effect. Results: Significant reductions in screen-time were observed in both groups from baseline to post-test (−51.2 min/day, p < 0.001 in the intervention group, −34.5 min/day, p = 0.021 in the control group, however the between group difference of −16.7 min/day was not statistically significant, p = 0.422). There were no significant intervention effects for any of the mental health outcomes, objectively measured physical activity or BMI. In both single and multiple mediator models, the intervention effect was partially mediated by increases in autonomous motivation to limit screen-time. Discussion: There was no intervention effect, as both the intervention and control groups reduced their screen-time over the study period. However, findings highlight the challenges of working to reduce screen-time among adolescents and highlight an urgent need to identify strategies to reduce screen-time based on the (83%) of 1107 students screened and exceeded screen-time guidelines. The non-significant intervention effects on screen-time were mediated by increases in autonomous motivation to limit recreational screen-time. As autonomous but not controlled motivation mediated such an effect, findings suggest a need to deal with intrinsic motivation which people integrate a value of an activity into their sense of self. This is a notable finding and highlights the potential for using SDT as a theoretical framework for screen-time reduction in adolescent populations.