Youth mental health is an important public health concern, with 10–20% of young people experiencing mental health problems worldwide, based on a WHO report of epidemiological data from several countries. 1 WHOThe world health report 2001—mental health: new understanding, new hope. World Health Organization, Geneva2001 Google Scholar Youth mental health is not merely the absence of disease: WHO defines it as a state of wellbeing that allows young people to learn and acquire education, have a positive sense of identity, manage their thoughts and emotions, have a fulfilling social life, and participate fully in society. 2 WHOMental health action plan 2013–2020. World Health Organisation, Geneva2013 Google Scholar Half of all mental illnesses start by the age of 14 years, making adolescence a crucial period for mental health promotion. 3 Kessler RC Berglund P Demler O Jin R Merikangas KR Walters EE Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry. 2005; 62: 593-602 Google Scholar Roles of cyberbullying, sleep, and physical activity in mediating the effects of social media use on mental health and wellbeing among young people in England: a secondary analysis of longitudinal dataMental health harms related to very frequent social media use in girls might be due to a combination of exposure to cyberbullying or displacement of sleep or physical activity, whereas other mechanisms appear to be operative in boys. Interventions to promote mental health should include efforts to prevent or increase resilience to cyberbullying and ensure adequate sleep and physical activity in young people. Full-Text PDF