The world's most respected medication associations have long recognised the validity of the hypnotic phenomenon and the effectiveness of hypnosis in therapeutic intervention. 

 

1892 - The British Medical Association (BMA) commissioned a committee to investigate hypnosis. Their report, published in the British Medical Journal, stated that they “satisfied themselves of the genuineness of the hypnotic state” and recognized that hypnotism is “frequently effective in relieving pain, procuring sleep, and alleviating many functional ailments.”

1955 -  A BMA subcommittee issued a report in the British Medical Journal endorsing the 1892 report and stating that hypnosis is a effective in treating psychosomatic disorders, revealing unrecognized motives and conflicts, removing symptoms, changing morbid thoughts
andbehaviors, and alleviating pain. The report also recommended that medical students be introduced to hypnosis as part of standard psychiatric training, and that specialists in psychology should receive instruction in hypnotism.

1958 -  The American Medical Association (AMA) approved a study by its Council on Mental Health, which recognized hypnotherapy as an orthodox medical treatment (as opposed to an “alternative” or “complementary” treatment). The AMA committee stated their agreement with the report of the BMA, and it recommended that instruction in hypnosis be included in the curricula of medical schools and postgraduate training centers. [In 1987 the AMA rescinded almost all policies from 1881–1958. As a result of that decision the AMA now has no official position on the use of hypnosis.] 

1960 - The American Psychological Association endorsed hypnosis as a branch of psychology (it should be understood that the practice of psychology emerged from the field of hypnosis)

1961 - The AMA Council on Mental Health recommended that medical students should receive 144 hours of training in hypnosis over a 9- to12-month period at the undergraduate and postgraduate levels. 

1978 - The Royal Society of Medicine (RSM) formed a section for “Hypnosis and Psychosomatic Medicine”.

1983 - The RSM approved a diploma level training course of hypnotherapy.

1984 - The RSM commissioned a report entitled “Symposium on Psychological Influences and Illness: Hypnosis and Medicine.”

1986 - The BMA emphasized that hypnotherapy is “part of orthodox medical treatment.” 

1995 - The United States’ National Institute of Health (NIH) issued an extensive report, which concluded that hypnosis is effective in alleviating chronic pain associated with cancer and other conditions, including irritable bowel syndrome (IBS) and tension headaches. 

2000 - BMA stated to the House of Lords Select Committee on Science and Technology that “Hypnotherapy and counseling may be considered as orthodox treatments.”

2001 - The British Psychological Society commissioned a group of psychologists to publish a report on The Nature of Hypnosis, which reported that hypnosis is a proven therapeutic medium. The report stated that “hypnotic procedures may be beneficial in the management and treatment of a wide range of conditions and problems encountered in the practice of medicine, psychiatry and psychotherapy.” 

2005 - The American Psychological Association published a formal definition of hypnosis.

Sources:
Kroger, W. (1977). Clinical and experimental hypnosis in medicine, dentistry, and psychology (2d ed.). Philadelphia: Lippincott. 

Robertson, D. (2000-2006). The Medical & Scientific Approval of Hypnotherapy. Retrieved November 30, 2015, fromhttp://www.rebhp.org/articles/Hypnosis-Medical-Scientific-Article.pdf