How long has it been around?

The ancients of many lands used hypnosis, especially in Asia and the Middle East. They usually used it on themselves, and usually without mysterious window-dressing. But hypnotism was introduced to popular culture by Franz Anton Mesmer (1734-1815). Mesmer was a sort-of-scientist, in a field which was the alchemy of his day, that of magnetism and electricity. He believed that the hypnotic state was an effect of magnetism, and set up some fairly hokey demonstrations that for a while seemed to have trendy France... well... mesmerized. Mesmer's demonstrations were quickly picked up by occultists and entertainment magicians, because people found it so interesting. Though Mesmer's theories were soon disproved, his fame caused scientists to study the phenomenon of hypnosis he was pointing to. In 1842, English eye scientist James Braid gave it the name 'hypnosis', from a Greek word for 'sleep'. Jean Charcot brought it to modern investigative scientific study, and Yale professor Clark Hull's work in the 1930s did much to develop a scientific understanding of it. Today, the study of hypnosis is closely tied into brain science. Since hypnosis changes the way the brain processes information, it can show us a lot about the patterns of certain activities in the brain, when matched to brain scans.

http://www.spirithome.com/hypnosis.html