In the Netherlands, child (mental) health care professionals screen for anxiety and depressive disorders in schoolchildren and adolescents and refer them to an effective intervention when needed. Screening is defined as the identification of a disease at an early stage or a previously unrecognized disease by the application of tests. Screening has two aims: a humanitarian and an economical aim. Although screening seems beneficial, it can cause harm as well. To prevent adverse consequences of screening, Wilson & Jungner described ten preconditions for screening in a public health setting. We scrutinized three of these preconditions in relation to the screening for an anxiety or depressive disorder in Dutch schoolchildren and adolescents, namely: 1) there must be an important health problem; 2) there must be a recognizable early symptomatic stage; and 3) there must be a suitable test. To examine whether anxiety and depressive disorders are important health problems in Dutch youth, we quantified the disease burden of anxiety and depressive disorders in 53,894 Dutch secondary school pupils. We quantified disease burden unadjusted and adjusted for comorbidities, as well as at individual and population level. At population level, both anxiety and depression yielded the greatest disease burden compared with eating disorders, substance use disorders, and somatic illnesses, and therefore, we concluded that anxiety and depressive disorders are important health problems for screening. Definitions of an early symptomatic stage of a depressive disorder are various: some describe it as transdiagnostic, while others describe it as moderate depression. In addition, the specific symptoms that play an important role in the development of a depressive disorder are still unknown. Therefore, we explored the association of age with 11 individual depression symptoms and 14 core anxiety symptoms and their interrelations in girls and boys separately. We found that depression symptoms showed more and/or stronger associations with ...