Can You Think Pain Away?
Expecting Pain Relief Triggers the Brain's Natural Painkillers, Study Shows
Aug. 23, 2005 -- When pain strikes, expecting relief from a drug may be a big help -- even if that drug has no active ingredients, a new study shows.
That quirk -- called the placebo effect -- is well known. It's why medicines are carefully compared to fake drugs, or placebos.
Now, researchers have used PET brain scans to show placebo power on pain relief. The study appears in The Journal of Neuroscience.
'Very Concrete' Finding
"Obviously, there is something very concrete going on behind the placebo effect, and we demonstrated that," researcher Jon-Kar Zubieta, MD, PhD, tells WebMD.
"It's actually what makes this study important," he continues. "We are able to now quantify these mechanisms [at] the level of chemistry of the brain, as opposed to just relying on subjective reports, which is what most people have done before," says Zubieta.
Zubieta is an associate professor of psychiatry, radiology, and neurosciences at the University of Michigan.
In the study, five healthy men in their 20s agreed to let researchers inject saltwater into their jaw muscles to bring mild pain. Then they were given a fake drug.
The men didn't know that the drug was phony. They were told that that they would get a drug that might or might not be active. They rated their pain and got PET brain scans.
The mere expectation that they were about to get a painkiller kicked the brain's internal pharmacy into gear. The men's brains released pain-suppressing brain chemicals called endorphins.
The placebo effect was greater in some men than in others.
"Some people experienced a very strong placebo effect," says Zubieta. He notes that those men released more endorphins than men with a weaker placebo effect.
The study also showed a link between expectations of pain relief, endorphins, and better mood despite pain.
"This is a pain model that lasts for 20 minutes. It's very mild; it's well tolerated," says Zubieta.
"But when you are experiencing pain for a relatively long period of time, your emotional state also becomes more negative. You become more irritable, you become more down, more fearful, and so forth," he continues.
"Those negative emotions also become suppressed by these peptides in the brain. So it's affecting multiple elements of the pain experience," says Zubieta.