ObjectivesTo systematically examine the evidence of harms and benefits relating to time spent on screens for children and young people’s (CYP) health and well-being, to inform policy.MethodsSystematic review of reviews undertaken to answer the question ‘What is the evidence for health and well-being effects of screentime in children and adolescents (CYP)?’ Electronic databases were searched for systematic reviews in February 2018. Eligible reviews reported associations between time on screens (screentime; any type) and any health/well-being outcome in CYP. Quality of reviews was assessed and strength of evidence across reviews evaluated.Results13 reviews were identified (1 high quality, 9 medium and 3 low quality). 6 addressed body composition; 3 diet/energy intake; 7 mental health; 4 cardiovascular risk; 4 for fitness; 3 for sleep; 1 pain; 1 asthma. We found moderately strong evidence for associations between screentime and greater obesity/adiposity and higher depressive symptoms; moderate evidence for an association between screentime and higher energy intake, less healthy diet quality and poorer quality of life. There was weak evidence for associations of screentime with behaviour problems, anxiety, hyperactivity and inattention, poorer self-esteem, poorer well-being and poorer psychosocial health, metabolic syndrome, poorer cardiorespiratory fitness, poorer cognitive development and lower educational attainments and poor sleep outcomes. There was no or insufficient evidence for an association of screentime with eating disorders or suicidal ideation, individual cardiovascular risk factors, asthma prevalence or pain. Evidence for threshold effects was weak. We found weak evidence that small amounts of daily screen use is not harmful and may have some benefits.ConclusionsThere is evidence that higher levels of screentime is associated with a variety of health harms for CYP, with evidence strongest for adiposity, unhealthy diet, depressive symptoms and quality of life. Evidence to guide policy on safe CYP screentime exposure is limited.PROSPERO registration numberCRD42018089483.

Background There is growing concern about associations between social media use and mental health and wellbeing amongst young people. We explored links between frequency of social media use and later mental health and wellbeing in early adolescents, including mediation of effects through cyberbullying and displacement of sleep and physical activity. Methods Secondary analyses of Our Futures, a nationally-representative longitudinal study of young people in England from age 13 to 16 years. Exposures: frequency of social media use at waves 1 (age 13/14 years) through 3 (age 15/16y). Outcomes: a) mental health: General Health Questionnaire (GHQ) at wave 2; b) wellbeing scores (life satisfaction, life is worthwhile, happiness and anxiety) at wave 3. Analyses adjusted for minimal sufficient confounding structure. Mediation: assessed using khb commands in Stata 15. Findings Very frequent social media use (habitually multiple times daily) increased from 42.6% (95% CI: 41.2, 44.2) in wave 1 to 68.5%(67.3, 69.7) by wave 3. Very frequent social media use in wave 1 predicted GHQ high score at wave 2 amongst girls (odds ratio (OR) 1.31 (95% CI: 1.06, 1.63) p=0.01) and boys (1.67 (1.24, 2.26) p=0.001). Persistent very frequent social media use across waves 1 and 2 predicted lower wellbeing amongst girls only (happiness 0.80 (0.70, 0.92) p=0.001; anxiety 1.28 (1.11, 1.48) p=0.001). Associations of social media use with GHQ high score and wellbeing scores for girls were attenuated when adjusted for cyberbullying, sleep and physical activity, although associations amongst boys remained significant. Interpretation Mental health harms related to very frequent social media use amongst girls and appeared very largely due to exposure to cyberbullying and or displacement of sleep and physical activity. Interventions to promote mental health should include efforts to prevent or increase resilience to cyberbullying and ensure adequate sleep and physical activity amongst young people.