In the BELLA study conducted by the Robert Koch Institute, approximately 5.4% of the examined children showed specific signs of depression. In addition to this relatively high prevalence of depressive disorders in childhood and adolescence, there is also a high likelihood of recurrence or chronicity of the disorder. This underscores the necessity for a diagnostic procedure that objectively and validly captures depressive symptoms in children and adolescents, as discussed in this book. The testing procedure should be applicable at short intervals and accurately reflect even the smallest changes in the severity of symptoms. The aim of the study, described in detail in the book, was to adapt an already existing, valid, and change-sensitive procedure from international adult diagnostics, the Montgomery-Asberg Depression Rating Scale (MADRS).