We experience trance states every day of our lives. When you are day-dreaming, in deep thought, or even watching television, you are in a trance. When you are going to sleep at night, you are in a trance. Trance states are observed in science by brainwave activity. These waves change when a person's brain becomes relaxed. A trance can be light, or very deep like deep sleep.
More than 200 years later, research in neuroscience is confirming at least parts of Mesmer’s outlandish theory. No, there is not magnetic fluid coursing through our bodies. But the power of mere suggestion — of imagination, as Franklin phrased it — is a more effective treatment than many modern skeptics might expect, causing real, measurable changes in the body and brain. Hypnotism has been shown to be an effective treatment for psychological problems, like phobias and eating disorders, but the practice also helps people with physical problems, including pain — both acute and chronic — and some gastrointestinal diseases. Physicians and psychologists have observed this with their own eyes for decades; now, many of them say that brain-imaging studies (not to mention the deep respect people tend to have for all things prefixed by “neuro”) are helping them finally prove their point.
Hence, the social constructionism and role-taking theory of hypnosis suggests that individuals are enacting (as opposed to merely playing) a role and that really there is no such thing as a hypnotic trance. A socially constructed relationship is built depending on how much rapport has been established between the "hypnotist" and the subject (see Hawthorne effect, Pygmalion effect, and placebo effect).
The American Society of Clinical Hypnosis (ASCH) is unique among organizations for professionals using hypnosis because members must be licensed healthcare workers with graduate degrees. As an interdisciplinary organization, ASCH not only provides a classroom to teach professionals how to use hypnosis as a tool in their practice, it provides professionals with a community of experts from different disciplines. The ASCH's missions statement is to provide and encourage education programs to further, in every ethical way, the knowledge, understanding, and application of hypnosis in health care; to encourage research and scientific publication in the field of hypnosis; to promote the further recognition and acceptance of hypnosis as an important tool in clinical health care and focus for scientific research; to cooperate with other professional societies that share mutual goals, ethics and interests; and to provide a professional community for those clinicians and researchers who use hypnosis in their work. The ASCH also publishes the American Journal of Clinical Hypnosis
It is used for a wide variety of applications, and studies into its efficacy are often of poor quality 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", that there is no evidence or insufficient evidence for efficacy.