The connection between the development of anesthesiology and pain therapy in the twentieth century is close. The optimistic idea to overcome pain by using general anesthesia derives from the nineteenth century. Treatment of nonsurgical pain remained in the background for a long time and innovations in pain medicine did not improve the insufficient care for patients with postoperative pain. Therapy of chronic pain was mainly surgical and the extreme of this surgical approach was psychosurgery. In the years following World War II leucotomy and lobotomy were established as methods to separate the psychological processing of pain from the experience of pain. Meanwhile, the French "pain surgeon" Ren, Leriche elaborated a theory of pain where chronic pain was no longer seen as a symptom but as a "douleur-maladie", a pain disease. His theory was considered on various occasions but did not gain acceptance before the 1950s. Research in anesthesiology, such as that conducted by the American scientist Henry Beecher separated psyche and physiology with respect to pathological pain. This was contrasted by the approach of clinical anesthesia to pain therapy, which was based on regional anesthesia. The first "pain clinics" were "nerve block clinics". John Bonica, a regional anesthesiologist, extended the framework of pain therapy by introducing multidisciplinary teamwork into the therapy of chronic pain. From today's viewpoint his 1953 monograph The Management of Chronic Pain is a milestone in the development of modern pain therapy. However, Bonica's work did not attain major importance until 1960 when he was appointed to a newly established chair. Gradually, chronic pain was recognized as an independent illness and differentiated as such from acute pain. In 1965 the gate control theory by Melzack and Wall offered a possible explanation for the mechanisms of chronic pain. By the end of the 1970s the spectrum was extended to the biopsychosocial approach which was foremost developed by the American psychiatrist George Engel, defined chronic pain as an illness rather than a disease. Concurrently, the radical behaviorism of the late 1960s affected both the therapy of chronic and of acute pain. Based on this theory, patient-controlled analgesia (PCA) was introduced in the 1970s and 1980s. Acute pain services (APS) in hospitals, were developed beginning in the 1980s using the continuous release of opioids. Regional anesthesia played a greater role than general anesthesia in developing pain therapy in the twentieth century and paved the way for pain therapy. The restriction to nerve blocks in pain centers was overcome by the expansion of theoretical foundations beyond the framework of anesthesiology. Impulses from psychology and psychosomatic medicine were crucial. The evolution of cancer pain therapy was distinct from non-cancer pain therapy.
