We do not think that we need to convince anybody who is interested in this textbook, no matter if it is a student, professional or interested non-professional, that a psychiatric disorder is a great burden for any adolescent or adult patient. Often it is however not only a burden for the patient, but it will also greatly affect their environment and thus most of society. Given that many psychiatric diseases are already present in childhood or adolescence, it is important that we improve our screening methods for these age-groups. We believe that children and adolescents who suffer from a psychiatric disease should all have access to adequate, up-to-date and evidence-based treatment possibilities to reduce their suffering and improve their functioning and quality of life. This will also reduce the burden that a psychiatric disease can put on all that are directly or indirectly involved, and thus ultimately on most of society. The most important aim of this textbook was therefor to provide up-to-date, evidence-based as well as responsible information regarding psychiatric diseases to help achieve this goal.