title: Intervention to reduce recreational screen-time in adolescents: Outcomes and mediators from the 'Switch-Off 4 Healthy Minds' (S4HM) cluster randomized controlled trial.
abstract: The primary objective was to evaluate the impact of the 'Switch-off 4 Healthy Minds' (S4HM) intervention on recreational screen-time in adolescents.
  
  
  
  Cluster randomized controlled trial with study measures at baseline and 6-months (post-intervention). Eligible participants reported exceeding recreational screen-time recommendations (i.e., >2h/day). In total, 322 adolescents (mean age=14.4±0.6years) from eight secondary schools in New South Wales, Australia were recruited. The S4HM intervention was 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 included mental health (i.e., well-being, psychological distress, self-perceptions), objectively measured physical activity, and body mass index (BMI). Outcome analyses were conducted using linear mixed models and mediation was examined using a product-of-coefficients test.
  
  
  
  At post-intervention, significant reductions in screen-time were observed in both groups, with a greater reduction observed in the intervention group (-50min/day versus -29min, p<0.05 for both). However, the adjusted difference in change between groups was not statistically significant (mean=-21.3min/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.
  
  
  
  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.
  
  
  
  ACTRN12614000163606.
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Mark.Babic@newcastle.edu.au.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Babic
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Jordan.Smith@newcastle.edu.au.
authors.forename: Jordan J
authors.initials: JJ
authors.lastname: Smith
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Philip.Morgan@newcastle.edu.au.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Morgan
authors.affiliation: Institute for Positive Psychology and Education, Australian Catholic University, Strathfield, NSW, Australia. Electronic address: Chris.Lonsdale@acu.edu.au.
authors.forename: Chris
authors.initials: C
authors.lastname: Lonsdale
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Ronald.Plotnikoff@newcastle.edu.au.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Plotnikoff
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Narelle.Eather@newcastle.edu.au.
authors.forename: Narelle
authors.initials: N
authors.lastname: Eather
authors.affiliation: Faculty of Science and IT, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Geoff.Skinner@newcastle.edu.au.
authors.forename: Geoff
authors.initials: G
authors.lastname: Skinner
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Amanda.Baker@newcastle.edu.au.
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Baker
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: Emma.Pollock@newcastle.edu.au.
authors.forename: Emma
authors.initials: E
authors.lastname: Pollock
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Newcastle, NSW, Australia. Electronic address: David.Lubans@newcastle.edu.au.
authors.forename: David R
authors.initials: DR
authors.lastname: Lubans
mesh_terms: D000293:Adolescent; D001315:Australia; D002648:Child; D002669:Child Welfare; D015444:Exercise / Q000502:physiology*; D015438:Health Behavior; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D057185:Sedentary Behavior; D013315:Stress, Psychological / Q000523:psychology; D013997:Time Factors
keywords: Physical activity; School; Screen; Sedentary behavior