Placebo: Not just in the mind

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Placebo: Not just in the mind

Research conducted at the University of Michigan in Ann Arbor provides concrete evidence of the mind-body connection through study of the placebo effect. Scientists have long been puzzled by questions of how and why some people, under certain circumstances, are able to achieve improved physical well-being simply through positive expectations. Many researchers have dismissed the placebo effect as an “imagined” or psychological phenomenon rather than a physical experience. The University of Michigan study shows that the placebo effect involves brain chemistry changes that affect pain receptors in the brain, resulting in a genuine physical experience of less pain.

“This deals another serious blow to the idea that the placebo effect is purely psychological,” said Jon-Kar Zubieta, MD, PhD, associate professor of psychiatry and radiology at the University of Michigan and research scientist at the university’s Molecular and Behavioral Neuroscience Institute. “We were able to see that the endorphin system was activated in pain-related areas of the brain, and that activity increased when someone was told they were receiving a medicine to ease their pain. They then reported feeling less pain. The mind-body connection is quite clear.”

In the study, researchers induced pain in 14 healthy male volunteers between the ages of 20 and 30 by injecting saltwater solution into their jaw muscles. As the injections were happening, researchers scanned the men’s brains to observe the pain response. During a second scan, researchers repeated the injections and then told subjects they would receive a medication (in fact, a placebo) that might relieve their pain.

All participants showed an increase in activation of the body’s natural pain relief response after they were told they would receive a pain-relieving medication and when the placebo was given. In nine participants, “high placebo responders,” pain signals dropped by more than 20%.

According to Zubieta and colleagues, this evidence that the expectation of pain relief begins to activate the body’s natural pain relief systems may help explain why so many people say they get relief from therapies and remedies that are not invasive and do not involve physical intervention. The researchers suggest that this evidence may promote better use of psychological therapy in treating people with chronic pain.

The study was published in The Journal of Neuroscience (2005; 25 (34), 7754–62).