Sleepwalking in Italian operas: a window on popular and scientific knowledge on sleep disorders in the 19th century.

There is little knowledge on sleepwalking in ancient times even though it is a very common condition. The aim of this report is to describe the backgrounds of medical knowledge on somnambulism in the 19th century, a key period in the development of neurosciences, by analysing its representation in two famous Italian operas: La Sonnambula by Vincenzo Bellini and Macbeth by Giuseppe Verdi. The 19th-century operas may be considered as a crossing point between the popular and intellectual world because they mirror popular answers to phenomena that were still awaiting scientific explanations. Shakespeare's play Macbeth was also considered. In Shakespeare's play and in Verdi's Macbeth, sleepwalking is looked upon as a neuropsychiatric disorder, a manifestation of internal anxiety. In La Sonnambula by Bellini, this condition is considered as common disorder that anticipates scientific theories. The analysed Italian operas provide two different views on sleepwalking, probably because they are based on texts belonging to different periods. Their examination allows one to understand the gradual evolution of theories on sleepwalking, from demoniac possession to mental disorder and sleep disease. At the same time, this analysis throws some light on the history of psychological illnesses.