The placebo effect, of course, is the well-known phenomenon in which patients who think they are getting medical treatment report that they feel better, even when they get only a sugar pill or other fake therapy.
Researchers in Hamburg, Germany, convinced 15 men to test a “lidocaine cream” that was strong enough to work as a local anesthetic. The researchers drew red and green boxes on the volunteers’ forearms. Then they applied the ointment to the green box and rubbed a “control cream” into the red box.
After waiting 10 minutes for the “lidocaine” to take effect, they applied a hot stimulus to one of the squares and kept it there for 20 seconds. Then they tested the other square. After each trial, the volunteers were asked to rate the intensity of their pain. The tests were repeated 14 more times.
As you may have guessed by now, the “lidocaine” and “control” creams were identical. And yet, the volunteers told researchers that the "lidocaine cream" reduced their pain by an average of 26%, the researchers report online today in the journal Science.
The scientists used functional MRI scans to track how the spinal cord responded to the painful stimuli. Sure enough, they detected less activity in the spinal cord when patients thought they were protected by the lidocaine.
The results show that a painful stimulus need not travel all the way to the brain to come under the influence of “psychological factors,” the researchers wrote. All it needs to do is reach the spinal cord – the first stop along the central nervous system – and the placebo effect will kick in.
-- Karen Kaplan