title: Decline in physical activity during adolescence is not associated with changes in mental health.
abstract: BACKGROUND
  The majority of studies investigating associations between physical activity and mental health in adolescents have been cross-sectional in design. Potential associations between physical activity and mental health may be better examined longitudinally as physical activity levels tend to decrease in adolescence. Few studies have investigated these associations longitudinally in adolescents and none by measuring physical activity objectively.
  
  
  METHODS
  A total of 158 Dutch adolescents (mean age 13.6 years, 38.6% boys, grades 7 and 9 at baseline) participated in this longitudinal study. Physical activity, depressive symptoms and self-esteem were measured at baseline and at the 1-year follow-up. Physical activity was objectively measured with an ActivPAL3™ accelerometer during one full week. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression Scale (CES-D) and self-esteem was assessed with the Rosenberg Self-Esteem Scale (RSE). Results were analysed using structural equation modelling.
  
  
  RESULTS
  Physical activity levels decreased 15.3% over a 1-year period (p < .001), with significantly (p = .001) greater decreases during grade 7 (-20.7%) than during grade 9 (-5.0%). Overall, depressive symptoms decreased (-12.1%, p < .001) over a 1-year period, while self-esteem did not change significantly (+2.9%, p = .066). Higher levels of depressive symptoms at baseline predicted a greater decline in depressive symptoms (β = -.51, p < .001) and higher levels of self-esteem at baseline predicted a smaller increase in self-esteem (β = -.48, p < .001). The decline in physical activity did not appear to predict any change in depressive symptoms and self-esteem.
  
  
  CONCLUSIONS
  The decline in physical activity over a 1-year period during adolescence is not associated with a change in mental health. Further studies in adolescents aiming to investigate whether a change in physical activity is associated with a change in mental health should control for baseline levels of mental health and academic year differences.
authors.affiliation: Welten Institute, Faculty of Psychology and Educational Sciences, Open University of the Netherlands, Heerlen, Netherlands. Martin.vanDijk@fontys.nl.|Fontys Sporthogeschool, School of Sport Studies, Fontys University of Applied Sciences, Eindhoven, The Netherlands. Martin.vanDijk@fontys.nl.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Van Dijk
authors.affiliation: Department of Human Movement Sciences, NUTRIM (School for Nutrition and Translational Metabolic Research), Maastricht University, Maastricht, The Netherlands.
authors.forename: Hans H C M
authors.initials: HHCM
authors.lastname: Savelberg
authors.affiliation: Faculty of Psychology and Educational Sciences, Open University of the Netherlands, Heerlen, Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Verboon
authors.affiliation: Welten Institute, Faculty of Psychology and Educational Sciences, Open University of the Netherlands, Heerlen, Netherlands.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Kirschner
authors.affiliation: Welten Institute, Faculty of Psychology and Educational Sciences, Open University of the Netherlands, Heerlen, Netherlands.|Department of Epidemiology & Complex Genetics, NUTRIM (School for Nutrition and Translational Metabolic Research), Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands.
authors.forename: Renate H M
authors.initials: RHM
authors.lastname: De Groot
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D003863:Depression / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008603:Mental Health; D009043:Motor Activity; D009426:Netherlands; D012649:Self Concept
keywords: Accelerometry; Depressive symptoms; Exercise; Self-esteem; The GOALS study; Youth