Hypnosis has been used as the sole anaesthesia for major surgeries since the 1800's. A study in JAMA reported that the National Institutes of Health panel issued a statement published by the American Medical Association in 1996 indicating that there was “strong evidence for the use of hypnosis in alleviating pain associated with cancer .” Another study showed that changes in the brain activity seen on functional magnetic resonance imaging (fMRI) suggest that hypnosis somehow blocks the pain signal from getting to the parts of the brain that perceive pain. A randomized, double-blind (for the use of naloxone) crossover study of patients with neuropathic pain found hypnosis provided considerable relief from pain, and this relief was not reversed by administration of naloxone. Yet another study found that hypnosis produced significantly better pain relief when compared with acupuncture and medications.

Some people believe that the changes seen after hypnotherapy are the result of the placebo effect. In order to study this hypothesis, hypnosis volunteers were evaluated by positron emission tomography (PET). When subjects were given the suggestion to see color, the color perception areas of their cerebral hemispheres were activated. This implies that hypnosis is not a process of simply following instructions but actually involves a change in the brain's perception . By using electroencephalography, changes were seen during hypnosis that could not be evoked by waking imagination.

One study used electrodermal skin conductance also showed that hypnosis involves more than just compliance with suggestions .

Activation of a region in the right anterior cingulate cortex, an area activated when sound is heard or when sound is suggested in hypnosis but not when sound is simply imagined. This implies that the mind registered the hypnotic suggestions as if it were real. Although the implications of these finding provide the theoretical basis for hypnosis, the most important factor is the results.

For a list of conditions for which hypnotherapy may be useful please scroll down to the 3rd paragraph. Please click the following link to view a brief description of journal articles supporting the effectiveness of hypnotherapy for these conditions.