Study by University of Pittsburgh and University College of London Shows People Under Hypnosis Feel Pain Similar to Those with Genuine Pain
PITTSBURGH, August 9, 2004 A brain imaging study by researchers at the University of Pittsburgh and the University College of London (UCL) exploring the experience of pain in hypnotized volunteers has provided new evidence for the basis of functional pain such as chronic low back pain, whose underlying physical cause continues to baffle doctors.
In the study, to be published in the journal NeuroImage, volunteers who were hypnotized into believing they felt pain showed strikingly similar brain activity to those subjected to genuine pain via pulses of heat at 48.5 degrees celsius (119 degrees fahrenheit), suggesting that some forms of pain which cannot be traced to a physical problem may have a neurological basis.
The study found that a third group of volunteers asked to imagine that they were experiencing the same pain had significantly lower brain activity than the hypnotized and genuine pain groups.
Stuart Derbyshire, Ph.D., assistant professor of anesthesiology and radiology at the University of Pittsburgh was principal investigator, along with David Oakley, Ph.D., director of UCLs Hypnosis Unit.
The study provides direct evidence of the brain generating pain in the absence of any actual noxious input, Dr. Derbyshire said. That is significant because many functional disorders, such as fibromyalgia, might rely upon similar mechanisms. We are currently running studies to test that idea with patients.
The researchers put eight subjects into a magnetic resonance brain scanner and took pictures of brain function while subjects were hypnotized. The subjects experienced periods of rest, periods of noxious heat delivered to the hand and periods when they were told the heat was coming but none was actually delivered.
During this latter period all the subjects reported still experiencing heat and most of these non-stimuli were experienced as painful. None of the subjects reported that they believed the probe was switched off, which in fact it was, Dr. Derbyshire said. Thus we were able to present images of the brain during an experience of pain based on actual delivery of a noxious stimulus and during a hypnotically induced experience of pain when no stimulus was actually delivered, he said.
Brain imaging is an objective way of exploring peoples own reported experiences of pain, because you cant easily fool a brain scanner, Dr. Oakley said. The fact that hypnosis was able to induce a painful experience suggests there is a neural network for pain in other words, some pain really could be in the brain.
Functional pain disorders such as chronic back pain, facial pain and fibromyalgia have no known underlying medical cause. Conversion disorders such as hysterical paralysis, where someone with a normal, healthy leg might be unable to move it, are just as poorly understood.