Systems theory, in this context, may be regarded as an extension of Braid's original conceptualization of hypnosis as involving "the brain and nervous system generally".[74](p31) Systems theory considers the nervous system's organization into interacting subsystems. Hypnotic phenomena thus involve not only increased or decreased activity of particular subsystems, but also their interaction. A central phenomenon in this regard is that of feedback loops, which suggest a mechanism for creating hypnotic phenomena.[183]
According to Dr. Clifford N. Lazarus, speaking for Psychology Today, hypnosis is a “genuine psychological phenomenon that has valid uses in clinical practice … hypnosis is a state of highly focused attention or concentration, often associated with relaxation, and heightened suggestibility. While under hypnosis (i.e., in a hypnotic trance), it seems many people are much more open to helpful suggestions than they usually are.” The suggestions made in a therapeutic setting get deep into a person’s brain, beyond their conscious thinking, leading to behavior change and the ability to overcome challenges that might otherwise seem insurmountable.
Jump up ^ Mauera, Magaly H.; Burnett, Kent F.; Ouellette, Elizabeth Anne; Ironson, Gail H.; Dandes, Herbert M. (1999). "Medical hypnosis and orthopedic hand surgery: Pain perception, postoperative recovery, and therapeutic comfort". International Journal of Clinical and Experimental Hypnosis. 47 (2): 144–161. doi:10.1080/00207149908410027. PMID 10208075.
The term "hypnosis" comes from the ancient Greek word ὕπνος hypnos, "sleep", and the suffix -ωσις -osis, or from ὑπνόω hypnoō, "put to sleep" (stem of aorist hypnōs-) and the suffix -is.[9][10] The words "hypnosis" and "hypnotism" both derive from the term "neuro-hypnotism" (nervous sleep), all of which were coined by Étienne Félix d'Henin de Cuvillers in 1820. These words were popularized in English by the Scottish surgeon James Braid (to whom they are sometimes wrongly attributed) around 1841. Braid based his practice on that developed by Franz Mesmer and his followers (which was called "Mesmerism" or "animal magnetism"), but differed in his theory as to how the procedure worked.
It would be difficult to find an area of scientific interest more beset by divided professional opinion and contradictory experimental evidence…No one can say whether hypnosis is a qualitatively unique state with some physiological and conditioned response components or only a form of suggestion induced by high motivation and a positive relationship between hypnotist and subject…T.X. Barber has produced "hypnotic deafness" and "hypnotic blindness", analgesia and other responses seen in hypnosis—all without hypnotizing anyone…Orne has shown that unhypnotized persons can be motivated to equal and surpass the supposed superhuman physical feats seen in hypnosis.[148]

It is used for a wide variety of applications, and studies into its efficacy are often of poor quality[2] which makes it difficult to determine efficacy. Several recent meta-analyses and systematic reviews of the literature on various conditions have concluded that the efficacy of hypnotherapy is "not verified",[3] that there is no evidence[4][5] or insufficient evidence[6][7] for efficacy.