Hamburg  - Contrary to conventional thought, the "placebo effect" may be effective in reducing chronic pain, German researchers report in the journal Science.

The placebo effect is often put down as merely psychological. The unconscious mind believes it is getting real help and rallies, even though the placebo itself does not contain anything helpful.

Now, German researchers report that when it comes to pain, the placebo effect affects activity in part of the spinal cord called the dorsal horn.

Falk Eippert and colleagues at Germany's University Medical Centre Hamburg-Eppendorf studied 15 healthy young men. First, the researchers applied heat to the men's arms in order to gauge their pain threshold.

Next, they treated the men's arms with two identical, inactive creams. But the researchers told the men that one of the creams was "an extremely effective painkiller" and that the other cream was a "control cream."

Finally, the researchers applied heat to the treated areas of the arms to stimulate the sense of pain.

When the men's arms were treated with the fake painkiller cream before being subjected to heat, they reported less pain than when their arms were treated with the control cream. In short, they were experiencing the placebo effect, just as the researchers had planned.

MRI scans taken during the tests showed less activity in the dorsal horn of the men's spinal cords, which is involved in sensory perception, when their arms had been treated with the fake painkiller cream.

The study does not explain the mind-body connection between the men's unconscious beliefs about the creams and how they responded to the pain from the heat. But the findings may open up "new avenues" for assessing the efficacy and action of new pain treatments, Eippert and colleagues write in Science. (dpa)