How hypnosis works

What Is Hypnotic Suggestion, and How Does It Change Behavior?

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A hypnotic suggestion is an idea offered during hypnosis that is meant to change what you feel, perceive or do: “your arm is becoming lighter,” “the craving passes like a wave,” “you stay steady when the plane takes off.” In a session, the induction, the relaxation and the quiet voice all lead up to the moment when a suggestion is given.

What forms can a suggestion take?

The Wikipedia article on hypnosis lists the range used in contemporary practice:

  • Direct verbal suggestions, which state the intended effect plainly.
  • Indirect verbal suggestions, delivered as requests or hints rather than statements.
  • Metaphors and other figures of speech, which carry the idea inside a story or image.
  • Non-verbal suggestions, through mental imagery, tone of voice or physical cues.

Practitioners also distinguish a permissive style (“you may notice your shoulders softening”) from an authoritarian one (“your shoulders are relaxing now”). The choice between direct and indirect forms tends to follow the practitioner’s theory of hypnosis. Those who think responses run mainly through an unconscious mind, following Milton Erickson, lean toward indirect suggestions and metaphor; those who think responses are mainly conscious, such as Theodore Barber and Nicholas Spanos, have tended to use direct instructions.

How does a suggestion reach everyday life?

Through post-hypnotic suggestions: ideas meant to take effect after the session ends. The Wikipedia article cites Harvard hypnotherapist Deirdre Barrett’s observation that suggestions in research studies are mostly designed to bring about immediate responses, while suggestions in hypnotherapy are usually post-hypnotic, intended to trigger changes in behavior for periods ranging from days to a lifetime. She adds that therapeutic suggestions are often repeated over several sessions before they reach their peak effect.

That is one reason hypnotherapy can run over a course of sessions rather than a single appointment, and why practitioners may also teach self-hypnosis: the suggestion has to show up in the situation that matters, such as the next craving or the next flight, not only in the therapy room.

Why would a suggestion change anything?

There is no single agreed answer. Three accounts from the history of hypnosis research are worth knowing.

The ideo-motor idea. James Braid borrowed his friend and colleague William Carpenter’s observation that merely thinking about a movement can produce a small, automatic movement. Braid extended it: the idea of sucking a lemon can start salivation. He called hypnotism a way of concentrating attention on a single idea to amplify that automatic response. Variations of this idea went on to shape later theories of hypnosis, including those of Clark Hull, Hans Eysenck and Ernest Rossi.

Heightened, less critical responsiveness. The same article describes a hypnotized person as typically responding in an uncritical, automatic fashion, perceiving in line with the hypnotist’s suggestions even when they contradict what is actually present. It also notes a general consensus that heightened suggestibility is an essential feature of hypnosis.

Expectation. Non-state researchers emphasize ordinary psychology, including response expectancy, a factor associated with Irving Kirsch. In 1994 Kirsch called hypnosis a “non-deceptive placebo”: a method that openly uses suggestion and works to amplify its effects.

These accounts are not mutually exclusive. In practice they point to the same conditions for a suggestion to work: focused attention, an idea the person can vividly imagine, and an expectation that it will take effect.

What can suggestion not do?

It does not work equally for everyone. Stanford Medicine reports that only about 10 percent of the population is generally categorized as highly hypnotizable, so a strong, effortless response to suggestion is the exception rather than the rule.

It can reach memory, which is a risk. The Wikipedia article notes that even memory and awareness of self may be altered by suggestion. That is the reason for caution with any attempt to use hypnosis to “recover” past events: a suggestion can shape what a person remembers, not only how they feel.

It is not a substitute for treatment. A suggestion can change how a symptom feels or how you respond to a trigger. It does not treat an underlying medical or psychiatric condition, which still needs its own assessment.

How to judge a suggestion-based approach

Ask the practitioner which suggestions they plan to use and why, how they will carry them into daily life between sessions, and how you will both know whether they are working. Good answers are specific: a named trigger, a rehearsed response, a measure you can track.

This article is general information, not medical or psychological advice; talk with a licensed clinician about your own situation.

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