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Associations between objectively measured physical activity and later mental health outcomes in children: findings from the UK Millennium Cohort Study
  1. Jane V Ahn1,
  2. Francesco Sera2,
  3. Steven Cummins2,
  4. Eirini Flouri1
  1. 1 Psychology and Human Development, University College London Institute of Education, London, UK
  2. 2 Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK
  1. Correspondence to Jane V Ahn, Psychology and Human Development, University College London Institute of Education, London WC1H 0AL, UK; jane.ahn{at}


Background The beneficial effect of physical activity (PA) on mental health in adults is well established, but less is known about this relationship in children. We examine associations between objectively measured sedentary time, PA and mental health in 11-year-olds from the UK Millennium Cohort Study (MCS).

Methods Longitudinal data from MCS sweeps 4 (age 7) and 5 (age 11) were used (n=6153). Accelerometer data were collected at MCS4, and mental health was measured at MCS4 and MCS5 using subscales (peer, emotional, conduct, hyperactivity) of the Strengths and Difficulties Questionnaire (SDQ). Associations between mean daily PA minutes at different intensities (sedentary, light, moderate-to-vigorous) at MCS4 and SDQ outcomes at MCS5 (score range 0–10) were estimated using multiple linear regression models, adjusting for SDQ at MCS4 and individual and family characteristics, and stratified by gender.

Results In fully adjusted models, increased PA at MCS4 was associated with fewer peer problems in boys and girls at MCS5. For each additional 15 min in moderate-to-vigorous physical activity (MVPA), peer problems decreased −0.077 points (95% CI −0.133 to –0.022) in boys. For girls, light PA was associated with decreased peer problems (−0.071 points/30 min, 95% CI −0.130 to –0.013). Greater sedentary time was associated with more peer problems and fewer hyperactivity symptoms in boys and girls. Increased MVPA was associated with more conduct and hyperactivity problems in boys and more hyperactivity in girls.

Conclusions Increased sedentary time is associated with more peer problems in children, and PA, generally, is beneficial for peer relations in children aged 11.

  • mental health
  • physical activity
  • child health
  • longitudinal studies
  • cohort studies

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  • Contributors JVA analysed the data, drafted and revised the paper. FS provided statistical support. FS, SC and EF revised the paper.

  • Funding The Millennium Cohort Study is funded by the Economic and Social Research Council (ES/M001660/1) and a consortium of government departments. Accelerometer data collection was funded by the Wellcome Trust (084686/Z/08/A). JVA is funded by a Bloomsbury Colleges PhD Studentship. FS is funded by a grant from UK Medical Research Council (MR/M022625/1).

  • Competing interests None declared.

  • Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.

  • Ethics approval Ethics approval for the MCS was obtained from a multicentre research ethics committee in the UK (ref: 11/YH/0203), National Health Service Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.