Childhood mental illness is poorly recognised by healthcare providers and parents, despite half of all lifetime cases of diagnosable mental illness beginning by the age of 14 years. Globally, depression is the leading cause of disease burden, as measured by disability-adjusted life years, in children aged 10-19 years. Untreated, it is associated with poor school performance and social functioning, substance misuse, recurring depression in adulthood and increased suicide risk, which is the second leading cause of preventable death among young people. The resulting cost to the National Health Service of treating depression is estimated at over £2 billion, and the wider social and economic impact of depression is likely to be considerable..