Brain activity changes during hypnosis, study finds

13 November 2009

Hypnosis is increasingly being used in clinical settings, as a way of helping people lose weight or stop smoking. The National Institute for Health and Clinical Excellence (NICE) recently approved the technique for treatment of irritable bowel syndrome, but despite such endorsements there is still a great deal of scepticism about whether there really is a hypnotic state.

New research from the University of Hull, published this week in Consciousness and Cognition, however shows that hypnosis is real. Psychologists have discovered that basic brain activity undergoes change when people are hypnotised.

Dr William McGeown and his colleagues in the department of Psychology and Centre for Clinical Neuroscience hypnotised university students and looked at brain activity, employing a technique called functional magnetic imaging (fMRI).

The research team included Professor Irving Kirsch, a world-known expert in hypnosis, Professor Annalena Venneri, an expert in brain imaging techniques and Professor Giuliana Mazzoni, an expert in suggestion and suggestibility.

Hypnosis studies usually require participants to do a task and researchers look at their brain activity during this time. In this experiment however, students’ brain activity was monitored in the rest periods between each task. This is the first time a hypnosis study has investigated brain activity in this manner; studying participants in rest whilst they are not performing any particular task.

The participants’ brain activity was also scanned without the hypnotic induction so that the resting states in and out of hypnosis could be compared.

The researchers first tested students for their ability to respond to a range of hypnotic suggestions, including suggestions to see a cat that was not there, to hear non-existent music, and to forget what had happened to them during the hypnotic session. They then invited subjects who could respond to these suggestions, and some that could not, to have their brains examined in an fMRI scanner while under hypnosis. Hypnosis altered anterior brain activity only in those subjects who were able to respond to suggestions. These are the people who may be termed “highly suggestible”.

The study led to the unexpected finding that hypnosis decreases activity in areas of the brain that support the so called “default mode” network. Activity in this network generally occurs when people are resting, day dreaming or letting their minds wander.

Dr McGeown says: “These results are unequivocal; the changes in anterior brain activity observed in our study occurred only in highly suggestible subjects, those most open to the idea of hypnosis. By contrast, no changes in brain activity were detected in these areas in the low suggestible subjects. This shows that the changes were due to hypnosis and not just simple relaxation.”

He concludes: “Our study shows that hypnosis is real; it corresponds to a unique pattern of brain activation which was not observed in any other experimental condition and was not seen in people who were not hypnotizable.”

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