Deep sleep therapy (DST), also called prolonged sleep treatment or continuous narcosis, is a discredited form of ostensibly psychiatric treatment in which drugs are used to keep patients unconscious for a period of days or weeks. The controversial practice led to the death of 25 patients in Chelmsford Private Hospital in New South Wales, Australia, from the early 1960s to late 1970s. History Induction of sleep for psychiatric purposes was first tried by Scottish psychiatrist Neil Macleod at the turn of the 20th century. He used sodium bromide to induce sleep in a few psychiatric patients, one of whom died. His method was adopted by some other physicians but soon abandoned, perhaps because it was considered too toxic or reckless. In 1915, Giuseppe Epifanio tried barbiturate-induced sleep therapy in a psychiatric clinic in Italy, but his reports made little impact. Electronarcosis was also developed and used for various psychiatric disorders, involving current passed through the brain to induce deep sleep. Deep sleep therapy was popularised in the early 1920s by Swiss psychiatrist Jakob Klaesi, using a combination of two barbiturates marketed as Somnifen by the pharmaceutical company Roche. Most of the patients that were treated had schizophrenia. The method became widely known and was used in some mental hospitals in the 1930s and 1940s. It was adopted and promoted by some leading psychiatrists in the 1950s and 1960s, such as William Sargant in the United Kingdom and by Donald Ewen Cameron, a North American psychiatrist of Scottish origin practising in Canada, some of whose research was funded by the Central Intelligence Agency (CIA) as part of their Project MKULTRA. Sargant wrote in his standard textbook An introduction to physical methods of treatment in psychiatry: Many patients unable to tolerate a long course of ECT, can do so when anxiety is relieved by narcosis ... What is so valuable is that they generally have no memory about the actual length of the treatment or the numbers of ECT used ... After 3 or 4 treatments they may ask for ECT to be discontinued because of an increasing dread of further treatments. Combining sleep with ECT avoids this ... All sorts of treatment can be given while the patient is kept sleeping, including a variety of drugs and ECT [which] together generally induce considerable memory loss for the period under narcosis. As a rule the patient does not know how long he