Is hypnosis a special brain state? Three new EEG studies disagree

The old debate

Researchers have long argued about whether hypnosis is a distinct state of consciousness (the “state” view) or ordinary attention and imagination shaped by expectation and context (the “non-state” view). EEG, which records the brain’s electrical activity through the scalp, is one way to test this. Three studies from the past year took different angles.

1. Does the label do the work?

One team ran each of 46 people with no hypnosis experience through four conditions. Two used a normal hypnotic induction and two used unusual “placebo” inductions. Each was labeled either as hypnosis or as a control task.^[1]

• The label mattered most for how deep people felt they went.
• One placebo induction, white noise called “hypnosis”, produced hypnosis depth ratings similar to real inductions.
• But another placebo induction produced shallower ratings, so not every procedure worked just by being labeled.
• The label itself had little effect on the EEG, and most brain measures were similar across all conditions. The most promising marker was lower gamma activity at the back of the head.

The authors say the results only partly support the idea that expectation is everything, and that confirmation studies are needed.^[1]

2. A shift within normal brain activity

Another group compared 16 people who respond strongly to hypnosis with 16 who barely respond. Only the strong responders experienced hypnosis as an altered state. Yet their brain network changes across the session followed a similar pattern to the low responders’.^[2]

The authors conclude that neutral hypnosis (hypnosis without specific suggestions) looks like a change within the normal range of waking brain activity rather than a distinct physiological state. The network measures they used did not explain why the two groups felt so different.^[2]

3. An active reorganization

A French study followed 23 people with medium-to-high hypnotizability through a hypnotic induction, recording EEG, heart rate and breathing. Changes unfolded in steps: first a drop in alpha activity and a rise in theta activity, then stronger theta connections between frontal and parietal areas, along with changes in heart rhythm.^[3]

The authors describe hypnotic induction as an active, high-arousal, top-down reorganization of large-scale brain networks. They also tested a suggestion that the arm was rigid. People reported similar loss of control over the arm, but some trembled while trying to bend it and others didn’t try at all, with different brain connectivity patterns in the tremblers.^[3]

The authors acknowledge their design can’t fully separate the induction from suggestion and expectation, and point to placebo-style designs like the first study as a better way to do that.^[3]

Why this matters in practice

If expectation and framing shape how deep hypnosis feels, then how a session is introduced matters, not just what is said during it. It also explains why good trials compare hypnosis against a convincing placebo. In a recent hot flash trial, white noise labeled as hypnosis cut hot flash scores by 41%, and real hypnosis still did better.

For the broader picture of what brain imaging has shown over the years, see what happens in your brain during hypnosis.