Placebos and drugs activate brain in pain relief. (Pregnancy & Birth).

Both placebos and strong painkillers activate the same areas of the brain, which suggests that pain relief may often be literally a case of mind over matter, researchers said in the February issue of Science. The experiment also suggests the brain has a built-in mechanism for dealing with pain.

Martin Ingvar of the Neurophysiology Research Group in Stockholm, Sweden, and colleagues there and in Finland exposed volunteers to painful heat and took scans of their brains to see what happened when the volunteers got painkillers or placebo injections of salt water.

"Placebo treatment and treatment with painkiller of the opioid family, they induced activity in the same region," Ingvar said.

"We had nine volunteers each with twelve scans," he said. The volunteers, who knew they were taking part in a pain study, had a heat probe taped to the backs of their hands. It could deliver anything from a warm glow to a 118 degree Fahrenheit near-burn.

The volunteers were told they would get one of two different injections for the pain, which led them to believe they were getting two drugs. In fact, they either got a fast-acting opioid drug, remifentanil, or plain saline.

While this was going on Ingvar's team took positron emission tomography (PET) scans of each person's brains. Pet scans can show brain cell activity. Both the drug and the placebo activated the same two areas of the brain--the rostral anterior cingular cortex and the brain stem.

"(This) indicated that we were actually able to get the same system spinning both with placebo and with the opioid," Ingvar said.

What was unexpected was that the people who responded most strongly to the drug also responded most strongly to the placebo injection, Ingvar said. Perhaps they have stronger pathways in the brain for pain relief, he guessed.

It is known that different people perceive pain in different ways and at different intensities.

The pain test used by the group is meant to standardize this as much as possible. "It's hot--you will be red for a few minutes afterwards," Ingvar said. "You'll pull your hand back if you are not aware it is part of an experiment."

Ingvar hopes the findings might help researchers find better ways to treat pain. Opioid drugs lose their effectiveness over time, causing patients to need larger and larger doses and eventually causing addiction.

Pain is a valuable mechanism, but once a person is aware of an injury, disease, or damage, and is taking care of it, pain loses its value.

"Pain, once you know it hurts, it's just pain," he said.

The study fits in with similar research reported in January that showed patients with depression who responded to either placebo or anti-depressant drugs had similar brain activity, as well.

This research supports the belief that many labor assistants and childbirth educators have used for years. Rather than advocating drugs for the pain of childbirth, labor assistants can use this mind over matter theory.

--Science, February 2002