Depression is a complex and multifaceted disease, that will commonly onset during adolescence. Those who experience an episode during adolescence are much more likely to experience future episodes throughout adolescence and later adulthood. Equally, they are much more likely to experience deficits in educational attainment, social functioning, along with a greater likelihood of poorer physical and mental health (including co-morbidities with other psychiatric traits and substance misuse). The overarching aim of this project is to quantify the burden of adolescent depression using the prospective data from the Avon Longitudinal Study of Parents and Children (ALSPAC). As a society, it is important to establish any links between depressive symptoms in childhood/adolescence and later deficits in early adulthood in order to inform public policies. This will help identify those who are at higher risk of encountering particular physical, psychosocial or economic problems in early adulthood and to ensure the necessary resources are in place for support.