Numerous birth-control studies, epidemiological studies, and observational studies investigated mental health and health care in childhood, adolescence and early adulthood, including prevalence, age at onset, adversities, illness persistence, service use, treatment delay and course of illness. Moreover, the impact of the burden of illness, of deficits of present health care systems, and the efficacy and effectiveness of early intervention services on mental health were evaluated. According to these data, most mental disorders start during childhood, adolescence and early adulthood. Many children, adolescents and young adults are exposed to single or multiple adversities, which increase the risk for (early) manifestations of mental diseases as well as for their chronicity. Early-onset mental disorders often persist into adulthood. Service use of children, adolescents and young adults is low, even lower than in adult patients. Moreover, there is often a long delay between onset of illness and first adequate treatment with a variety of linked consequences for poorer psychosocial prognosis. This leads to a large burden of illness with respect to disability and costs. As a consequence several countries have implemented so-called "early intervention services" at the border of child and adolescent and adult psychiatry. Emerging studies show that these health care structures are effective and efficient. Part 2 of the present review focuses on illness burden including disability and costs, deficits of the present health care system in Germany, and efficacy and efficiency of early intervention services.
