What Is Hypnosis? Suggestion Without the Stage Show

A typical procedure has two parts. An induction focuses attention and reduces awareness of surroundings, usually through relaxation instructions, fixation on an object or guided imagery, though inductions that involve no relaxation at all work comparably, which is itself evidence that relaxation is not the mechanism. Then come suggestions, statements inviting an altered experience, ranging from simple motor effects such as an arm feeling heavy, through perceptual changes such as not feeling a stimulus, to more complex suggestions about memory or behaviour. The person remains awake, aware and in control, brain activity does not resemble sleep, and people can and do decline suggestions they find objectionable, which is why the fear of being made to do something against one's values does not survive examination. Responses vary enormously between individuals, and that variation is the most robust finding in the whole field.

Hypnotic suggestibility is measured with standardised scales that administer a fixed series of suggestions and count responses, and the resulting distribution is stable and consequential:

• •Roughly ten to fifteen percent of people score highly, responding to most suggestions including perceptual and memory ones
• •The majority score in the middle, responding to some suggestions and not others
• •Roughly ten to fifteen percent score low and respond to very little, which no amount of technique reliably changes
• •Scores are stable over decades, with test-retest reliability comparable to intelligence measures, which makes suggestibility look like a trait rather than a state
• •High suggestibility does not correlate with gullibility, compliance or weak will, which is the popular assumption and is not supported
• •It does correlate modestly with absorption, the tendency to become deeply engaged in imagination, reading or music, and there is evidence of a genetic component

Clinical evidence is strongest for pain. Hypnosis reduces experienced pain in controlled studies of experimental pain, procedural pain, childbirth and chronic conditions, with effects that are not explained by relaxation alone, and brain imaging shows reduced activity in regions processing the emotional dimension of pain rather than in the sensory pathway itself, which fits the reports of patients who say they can feel the sensation without minding it. Hypnosis has been used as the sole anaesthetic in surgery in documented cases, mostly in highly suggestible patients. It has solid evidence in irritable bowel syndrome, where gut-directed hypnotherapy is recommended in several clinical guidelines, and reasonable evidence for anxiety around procedures, for some skin conditions and as an adjunct to smoking cessation and behavioural treatments. The pattern is that it works best as an addition to established treatment and for conditions in which the experience of a symptom is a substantial part of the problem.

The clearest failure is memory. Hypnosis does not improve recall accuracy, and it reliably increases confidence in whatever is recalled, including material that is false, which is the worst possible combination. Hypnotically refreshed testimony has been excluded or restricted by courts in many jurisdictions for exactly that reason, and the wave of recovered memory cases in the 1980s and 1990s, in which people came to believe in abuse that had not occurred, involved suggestive techniques including hypnosis and caused enormous damage to families and to the credibility of therapy. Age regression does not return a person to a childhood state and produces behaviour that resembles an adult's idea of childhood. The theoretical debate about what hypnosis is remains open, between accounts treating it as an altered state involving dissociation of executive control and accounts treating it as ordinary social and cognitive processes operating with unusual force, and both make similar predictions about most findings. Stage hypnosis depends on selecting the small minority of highly suggestible volunteers, along with social pressure and willing participation.

Hypnosis is a procedure of focused attention followed by suggestions, with the person awake, aware and able to refuse. Suggestibility is a stable trait, high in roughly a tenth of people and low in another tenth, and unrelated to gullibility or weak will. It has solid evidence for pain, where imaging shows it dampens the emotional rather than the sensory dimension, and for irritable bowel syndrome. It does not improve memory accuracy and does increase confidence in false recollections, which is why courts restrict hypnotically refreshed testimony.