[The contributions by Emil Kraepelin to the knowledge on sleep disorders and their treatment].

While Emil Kraepelin's comprehensive psychiatric oeuvre has attracted researchers' attention, his studies on sleep disorders and their treatment as well as on the interconnections between sleep and mental disorders so far seem to have been neglected.This article identifies and analyzes Kraepelin's sporadic contributions on the pathology of sleep, the comorbidities and treatment made between 1883 and 1924 in textbooks and isolated papers as well as in a presentation that was also published and compares them with current opinions in sleep research.Kraepelin never published a dedicated work on sleep, apart from a summary of the different narcotics; however, his occasional statements reveal astonishing insights and in particular his clear etiologically oriented classification of sleep disorders is captivating. Similar to the current classification, Kraepelin conceptualized sleep disorders as symptoms or rather a complex of symptoms and also identified associated diseases which once again are very near to current opinion. Apart from this his recommendations on sleep hygiene and, in a second step, pharmacological treatment of pathological sleep patterns are still clinically relevant. As early as the end of the nineteenth century Kraepelin laid down an algorithm of treatment which is very similar to the current clinical guidelines. At Kraepelin's time it seemed impossible to reach an agreement on classification and treatment issues of sleep disturbances and even though there has been an ongoing discussion until the present day, an agreement at least about guidelines could be reached. Against this background Kraepelin's contributions can still be regarded as a proposal for best practice.