Introduction

Trends in child and adolescent mental health can be seen as a barometer of the success of society's efforts to improve children's well-being and life chances. Improving the mental health of children was identified as a key strategic target in The Children's Plan (DCSF, 2007a). In this context, evidence of long-term deterioration in the mental health and behavioural adjustment of young people (Rutter and Smith, 1995; Maughan et al, 2005), and unfavourable comparisons with child well-being in other countries (UNICEF, 2007), has provoked significant concern among policy makers and health professionals in the UK (see, for example, Layard and Dunn, 2009).

Child and adolescent mental health problems are common and often have long-lasting and far-reaching consequences for children's lives. Large, well-designed epidemiological studies demonstrate that at any one time approximately one in ten of Britain's 5- to 16-year-olds suffers from a clinically impairing psychiatric disorder (Meltzer et al, 2000; Green et al, 2005). Depression, anxiety, conduct disorder and attention deficit hyperactivity disorders (ADHDs) are all common, with wideranging associated functional impairments. They affect children and adolescents’ educational progress, relationships with friends, family life and physical health.

The focus of this report is on trends in adolescent mental health (although comparisons are drawn where relevant with what is known about trends in younger children's mental health). The reason for this focus is that adolescence is an important risk period for the onset of mental health problems. The prevalence of many mental health problems, including depression and anxiety, increases sharply during adolescence (see Figure 2.1).

Moreover long-term prospective follow-up studies highlight strong continuities between adolescent and adult mental health. More than half of all early adult psychiatric disease is preceded by mental illness before the age of 18 (Kim-Cohen et al, 2003); conversely, adolescents with anxiety or depression are at substantially increased risk for adult psychiatric illness. Adolescent depression, for example, is highly recurrent, with 50-70 per cent showing future episodes of depression in adulthood (Lewinsohn et al, 1998). Depression is associated with significant morbidity and mortality, and suicide is the second or third leading cause of death among adolescents (Thapar et al, 2010).