According to the American Psychological Association's Division 30, hypnosis may bring about "...changes in subjective experience, alterations in perception, sensation, emotion, thought or behavior. The hypnotic state may also facilitate change in the body: it has been successfully used as a treatment for irritable bowel syndrome, as an alternative to chemical anaesthesia, and it has been studied as a way to soothe skin ailments.
Skeptics point out the difficulty distinguishing between hypnosis and the placebo effect, proposing that the state called hypnosis is
"so heavily reliant upon the effects of suggestion and belief that it would be hard to imagine how a credible placebo control could ever be devised for a hypnotism study."
Self-hypnosis is popularly used by people who want to quit smoking and reduce stress, while stage hypnosis can be used to persuade people to perform unusual public feats.
Franz Mesmer in the 1700's believed that there was a magnetic fluid that surrounds the body. He experimented with magnets to influence this field and so cause healing. He later found that the same effects could be created by waving the hands in front of someone's face. Although his theories were later discredited, the effects he was able to achieve with subjects may shed light on modern day hypnosis. Franz Mesmer is where the word mesmerize originated.
The word 'hypnosis' itself is the invention of 19th century Scottish physician James Braid.
Hypnosis has been studied in many clinical situations with varying degrees of success. It has been used as a painkiller, an adjunct to weight loss, a treatment of skin disease, and a way to soothe anxious surgical patients. It has also been used as part of psychological therapy, a method of habit control, a way to relax, and a tool to enhance sports performance.
A large number of clinical studies show that hypnosis can reduce the pain experienced by people undergoing burn-wound debridement, bone marrow aspirations, and childbirth. The International Journal of Clinical and Experimental Hypnosis found that hypnosis relieved the pain of 75% of 933 subjects participating in 27 different experiments.
In 1996, the National Institutes of Health declared hypnosis effective in reducing pain from cancer and other chronic conditions. Nausea and other symptoms related to incurable diseases may also be controlled with hypnosis. For example, research done at the Mt. Sinai School of Medicine studied two groups of patients facing surgery for breast cancer. The group that received hypnosis reported less pain, nausea, and anxiety post-surgery. There was a cost benefit as well: the average hypnosis patient reduced the cost of treatment by an average of $772.00.
Hypnosis may be useful as an adjunct therapy for weight loss. A 1996 meta-analysis studying the effectiveness of hypnosis combined with cognitive-behavioral therapy found that people using both treatments lost more weight than people using CBT alone.
Self-hypnosis is said to be a skill one can improve as time goes by, and can help reduce stage fright, promote relaxation, and enhance physical well-being.
Hypnotherapy is the use of hypnosis in psychotherapy. It is used by licensed physicians, psychologists, and in stand-alone environments. Physicians and psychiatrists may use hypnosis to help treat depression, anxiety, eating disorders, sleep disorders, and posttraumatic stress disorder.
Certified hypnotherapists who are not physicians or psychologists often do treatments for smoking cessation and weight loss. (Success rates vary: a meta-study researching hypnosis as a quit-smoking tool found it had a 20 to 30 percent success rate, similar to many other quit-smoking methods, while a 2007 study of patients hospitalized for cardiac and pulmonary ailments found that smokers who used hypnosis to quit smoking doubled their chances of success.)
In a July 2001 article for Scientific American titled "The Truth and the Hype of Hypnosis", Michael Nash wrote that "...using hypnosis, scientists have temporarily created hallucinations, compulsions, certain types of memory loss, false memories, and delusions in the laboratory so that these phenomena can be studied in a controlled environment."
Controversy surrounds the use of hypnotherapy to retrieve repressed or past-life memories. The American Medical Association and the American Psychological Association have cautioned against the use of repressed memory therapy in cases of alleged childhood trauma, stating that "it is impossible, without other corroborative evidence, to distinguish a true memory from a false one." Past life regression, meanwhile, is often viewed with skepticism.
Stage hypnotism is a form of entertainment for crowds. Due to stage hypnotists' showmanship, many people believe hypnosis is a sort of mind control. However, the real power of stage hypnosis comes from people granting hypnotists the ability to take over their critical thinking. The desire to be the center of attention, having an excuse to violate their own inner fear suppressors and the pressure to please are thought to convince subjects to 'play along'.
Influencing crowds through common longings and yearnings by a demagogue is called "mass hypnosis." "Religious trance" can be brought about through music and dance.
Post-hypnotic suggestion can be used to change people's behavior outside of the trance state. One author wrote that "a person can act, some time later, on a suggestion seeded during the hypnotic session...A hypnotherapist told one of his patients, who was also a friend: 'When I touch you on the finger you will immediately be hypnotized.' Fourteen years later, at a dinner party, he touched him deliberately on the finger and his head fell back against the chair.
Some psychologists, such as Robert Baker and Graham Wagstaff, claim that what we call hypnosis is actually a form of learned social behaviour, a complex hybrid of social compliance, relaxation, and suggestibility that can account for many esoteric behavioral manifestations.
Nicholas Spanos states, "hypnotic procedures influence behaviour indirectly by altering subjects' motivations, expectations and interpretations."
The team screened subjects before the study and chose 12 that were highly susceptible to hypnosis and 12 with low susceptibility. They all completed the task in the fMRI under normal conditions and then again under hypnosis.
Throughout the study, both groups were consistent in their task results, achieving similar scores regardless of their mental state. During their first task session, before hypnosis, there were no significant differences in brain activity between the groups.
But under hypnosis, Gruzelier found that the highly susceptible subjects showed significantly more brain activity in the anterior cingulate gyrus than the weakly susceptible subjects. This area of the brain has been shown to respond to errors and evaluate emotional outcomes.
The highly susceptible group also showed much greater brain activity on the left side of the prefrontal cortex than the weakly susceptible group. This is an area involved with higher level cognitive processing and behaviour.