Sleep and Dreams: From Myth to Medicine in Ancient Greece

• Hypnos and Oneiroi, gods of sleep and dreams, associated to oblivion and pain.
• Sleep induction, enkoimesis, a healing practice in the sanctuaries of Asklepios.
• “Euthanasia”, as voluntary permanent sleep, was known in ancient Greece.
• Greek physicians considered sleep and dreams as biological phenomena.
• Hippocratic physicians used sleep and dreams for medical prognosis and diagnosis.

Starting from the epic poems of Homer and Hesiod in the 8th century bce, the significance attributed to sleep and dreams by Greek antiquity is traced in myths referring to the god of sleep, Hypnos, and the dream gods, the Oneiroi. Hypnos was related to very ancient deities of darkness; his mother Nychta (night), his twin brother Thanatos (death) and his sons the Oneiroi (dreams) who dwelled “past the gates of the dead.” Early in the 6th century bce, induced sleep, enkoimesis or dream incubation, became an established healing practice in the sanctuaries of Asklepios. ⁎ Later, starting in the 4th century bce, sleep and dreams were among a series of biological phenomena that became an integral part of the Greek physician's practice. Several Hippocratic treatises explore the medical significance of sleep and dreams, as symptoms of disease. The treatise On Regimen IV uses dreams as prognostic and diagnostic signs of normal or abnormal internal conditions. This treatise distinguishes two types of dreams, those sent by the gods and those sent by the soul. The soul observes the body during sleep and informs on any impending problem manifested by dreams. By interpreting patients' dreams, the Hippocratic physician made a prognosis about the condition of the patient's body, the effects of diet and physical exercise, and adjusted the regimen to prevent deterioration of disease. It is the study of sleep and dreams in ancient Greece that provides us with knowledge on the evolution of these notions from mythology to medicine.