SHELLEY WU, PhD

Mind-Body Wellness Coach
Registered Yoga Teacher E-RYT500

Pain Reduction by Hypnosis:
Brain Imaging Studies

You might have heard that hypnosis can provide comfortable birth to women and ease pain in burn victims. But do you know how hypnosis reduces pain?

Researchers at University of Iowa and the Technical University of Aachen, Germany used functional magnetic resonance imaging (fMRI) and found that hypnosis alters brain activity in a way that might explain pain reduction by hypnosis.

The researchers found that volunteers under hypnosis experienced significant pain reduction in response to painful heat. They also had a distinctly altered pattern of brain activity compared to when they experienced the painful heat while not in hypnosis. The brain activity imaging suggests that hypnosis somehow blocks the pain signal from reaching the parts of the brain that perceive pain.

"The major finding from our study, which used fMRI for the first time to investigate brain activity under hypnosis for pain suppression, is that we see reduced activity in areas of the pain network and increased activity in other areas of the brain under hypnosis," said Sebastian Schulz-Stubner, M.D., Ph.D., UI assistant professor (clinical) of anesthesia and first author of the study. "The increased activity might be specific for hypnosis or might be non-specific, but it definitely does something to reduce the pain signal input into the cortical structure."

The Experiment

1. Twelve volunteers at the Technical University of Aachen had a heating device placed on their skin to determine the temperature that each volunteer considered painful (8 out of 10 on a 0 to 10 pain scale).

2. The volunteers were then split into two groups.
Group #1: The fMRI twice scanned their brain activity while the same painful heat was applied, first under hypnosis, then out of hypnosis.
Group #2: The fMTI scan was used first without hypnosis, then under hypnosis.

Pain Reduction Results

1. Perception of Pain

Hypnosis was successful in reducing self-reported pain perception for all 12 participants. Hypnotized volunteers reported either no pain or significantly reduced pain (less than 3 on the 0-10 pain scale) in response to the painful heat.

2. Brain Activity Under Hypnosis as Shown in fMRI Scan

As explained in the University of Iowa news release, the pain network functions "like a relay system with an input pain signal from a peripheral nerve going to the spinal cord where the information is processed and passed on to the brain stem. From there the signal goes to the mid-brain region and finally into the cortical brain region that deals with conscious perception of external stimuli like pain." The fMRI imaging in this study showed:

• Processing of the pain signal through the lower parts of the pain network looked the same in the brain images for both hypnotized and non-hypnotized trials.
• Under hypnosis, brain activity was reduced in areas of the pain network, including the primary sensory cortex, which is responsible for pain perception.
• Under hypnosis, brain activity was increased in the left anterior cingulate cortex and the basal ganglia, which lead to the speculation these two regions may be part of an inhibition pathway that blocks the pain signal from reaching the higher cortical structures.

More detailed brain activity images generated by more advanced fMTI machines are needed to definitively identify the exact areas involved in hypnosis-induced pain reduction.

"Imaging studies like this one improve our understanding of what might be going on and help researchers ask even more specific questions aimed at identifying the underlying mechanism," Schulz-Stubner said. "It is one piece of the puzzle that moves us a little closer to a final answer for how hypnosis really works. "More practically, for clinical use, it helps to dispel prejudice about hypnosis as a technique to manage pain because we can show an objective, measurable change in brain activity linked to a reduced perception of pain," he added.

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