( en. The most pronounced differences wer...)Thinking the pain away? Study shows the brain's painkillers may cause 'placebo effect'

When the researchers correlated the mu opioid activity changes with the participants' own ratings of their pain and emotions, they also observed that the placebo-induced activation of the opioid system was correlated with various elements of the experience of pain.

For example, activity in the dorsolateral prefrontal cortex was associated with the expectation of pain relief reported by the volunteers. In other areas, that activation was associated with relief of the intensity of pain, how unpleasant it was, or even how the individuals felt emotionally during the pain experience.

Because the new study was done only in healthy men between the ages of 20 and 30, further research will be needed to determine whether the effect occurs in women and in people with various illnesses. The power of placebos to ease pain symptoms has been well-documented in many groups of subjects and illnesses, but the researchers started with healthy young males to rule out the impact of chronic pain, mood disorders and hormone variations, which can also affect the endorphin system.

In addition to Zubieta, the research team included MBNI members Joshua Bueller, Lisa Jackson, David Scott and Janyun Xu; radiology professor Robert Koeppe, Ph.D.; Thomas Nichols, Ph.D., an assistant professor of biostatistics in the U-M School of Public Health; and Christian Stohler, formerly of the U-M School of Dentistry and now at the University of Maryland School of Dentistry.