Hypnosis and suggestion

What it is

A procedure in which a practitioner offers suggestions that a subject experiences as involuntary changes in perception, sensation, memory, mood or behaviour.

The essential and frequently misunderstood point is that the effects belong to the subject, not the hypnotist. Responsiveness varies enormously between people and is a stable, measurable trait — around ten to fifteen per cent of people are highly hypnotisable, a similar proportion barely respond at all, and the rest sit between. Standardised scales for measuring this have existed since the 1950s.

Where it came from

Franz Anton Mesmer in 1770s Vienna and Paris, with the theory of animal magnetism — an invisible fluid whose blockage caused illness and whose redirection cured it. His treatments produced dramatic crises and cures, and he was extremely popular.

In 1784 Louis XVI appointed a royal commission to investigate. Its members included Benjamin Franklin, then in Paris, and Antoine Lavoisier. Their method was to separate the claimed cause from its context: subjects were "magnetised" without knowing it, and told they were being magnetised when they were not. The effects followed belief, not the fluid.

The commission's report concluded the fluid did not exist and that the effects were produced by imagination. It is the first blinded, placebo-controlled experiment in the history of medicine, and it was conducted on a metaphysical claim.

Mesmer's theory died. The phenomenon did not. James Braid in the 1840s renamed it hypnotism and gave it a psychological rather than fluidic account. Jean-Martin Charcot used it at the Salpêtrière on hysteria, where the young Freud saw it. Milton Erickson in the mid-twentieth century developed the indirect, conversational style from which clinical hypnotherapy and much of modern psychotherapy's language descend.

How it is done

Through an induction — focused attention, relaxation, imaginative absorption — followed by suggestions. This article does not instruct.

What we can and cannot say

We can say the effects are real and measurable. Hypnotic analgesia is the strongest case: suggested pain reduction produces changes in the brain's pain-processing regions, works in burns dressing changes and in some surgical procedures, and outperforms attention control conditions. Hypnosis has trial evidence — including Cochrane-level review — for irritable bowel syndrome, procedural pain and anxiety, and some support in smoking cessation and labour. It is used in real hospitals by real anaesthetists.

We can say there is no hypnotic trance state that brain imaging has cleanly identified, and this is contested. One camp holds hypnosis is a distinct altered state; another — the sociocognitive tradition of Theodore Barber, Nicholas Spanos and Irving Kirsch — holds that it is ordinary suggestion, expectancy and role enactment, requiring no special state. Imaging shows changes during hypnosis, but showing that suggestion changes the brain is not the same as showing a state exists. The argument is fifty years old and unresolved.

We can say nobody can be made to do what they would refuse. Stage hypnosis works on volunteers who have already chosen to be on a stage, with strong situational pressure to comply. The "hypnotised assassin" is fiction.

And we can say the memory findings are the most consequential thing here, and they run one way. Hypnosis does not improve the accuracy of recall. It reliably increases confidence, and it increases the production of detailed false memories, which the person then holds with certainty. This is settled, and it has legal consequences: hypnotically refreshed testimony is inadmissible or severely restricted in many jurisdictions.

That finding demolishes a category of claim that appears repeatedly elsewhere on this site. Past-life regression produces vivid, detailed, emotionally convincing narratives that trace, where they have been checked, to forgotten ordinary sources — the classic case being "Bridey Murphy" in 1950s Colorado, whose Irish memories were traced to a neighbour of the subject's childhood. Recovered memories of abuse obtained under hypnosis were at the centre of the satanic ritual abuse panic and destroyed families. Alien abduction narratives were substantially produced by hypnotic interview by investigators who already believed. In each case the sincerity of everyone involved is not in question, and the memories are not reliable.

We can say the same mechanism explains a good deal of what looks like something else. Suggestion, expectancy and absorption account for much of what is reported from healing services, from energy work, from group ritual, and from some high-demand group practice. It is not a debunking so much as a common cause.

We cannot say what hypnosis is at the level of mechanism. What we can say is that the first controlled trial in medical history was run on this, in 1784, by Franklin and Lavoisier, and that they got the answer right.

Further reading

• The 1784 Franklin Commission report — short, readable, and remarkable.
• Irving Kirsch on response expectancy.
• Elizabeth Loftus's work on memory construction, which is the essential background.