Placebo effect on brain can ease some pain

Researchers find that the expectation of pain relief can trigger brain changes on a molecular level.

By Susan J. Landers, AMNews staff. Sept. 26, 2005.

Washington -- When it comes to the placebo effect and pain relief, the brain appears to be a much more active player than has been recognized up to now.

Not only does the brain stem play a role, but the cognitive areas of the brain also get involved, according to a study published in the Aug. 24 Journal of Neuroscience. Parts of the brain that effect such complex activities as thought, emotion, reward and response to pain are all activated when a person thinks that pain relief is on the way, said Jon-Kar Zubieta, MD, PhD, lead author and an associate professor of psychiatry and radiology at the University of Michigan Medical School.

This conclusion adds to a growing body of evidence that the placebo effect is very real and that better use of cognitive therapies might lead to more effective treatments for people with chronic pain.

The study also gives direct evidence that endorphins play a vital role in the placebo effect. "We were able to see that the endorphin system was activated in the brain's pain-related areas, and that activity increased when someone was told they were receiving a medicine to ease their pain," Dr. Zubieta said. "They then reported feeling less pain. The mind-body connection is quite clear."

The findings are based on sophisticated brain scans of 14 young, healthy men who agreed to allow researchers to inject their jaw muscles with a concentrated salt water solution to cause pain. The injection was made while they were having their brains scanned by a positron emission tomography scanner. During one scan they were told they would receive a medicine that might relieve pain. The medicine was actually a placebo.