Scans Show Placebo Acts on Brain's Pain Center
Thu Feb 7, 5:30 PM ET
By Merritt McKinney

NEW YORK (Reuters Health) - In a finding that challenges a recent report suggesting that the placebo effect is not real, researchers have found that an inactive medication can influence the same part of the brain affected by pain-killing drugs.


Placebos seem to provide pain relief by activating brain pathways that are known to be involved in pain control, Dr. Martin Ingvar of the Cognitive Neurophysiology Research Group in Stockholm, Sweden, told Reuters Health.

"Hence, this sort of placebo effect is not something fishy," Ingvar said.

The placebo effect occurs when people on an inactive drug or therapy experience improvement in their symptoms. Researchers compare new drugs to placebo to gauge the true benefit of a therapy.

Last year, Danish researchers published a report asserting that the placebo effect is for the most part a myth.

But in a report in the February 7th issue of Sciencexpress, the online edition of the journal Science, Ingvar and his colleagues provide evidence that the placebo effect is not just a figment of patients' imaginations.

The researchers used an imaging test called positron emission tomography to evaluate people's reactions to a series of painfully hot and non-painful warm sensations. During the experiments, participants received an opioid painkiller, placebo or nothing at all.

Participants experienced pain relief while taking the painkiller or placebo, and in both situations, activity increased in a part of the brain called the rostral anterior cingulate cortex (ACC). The ACC is thought to be involved in controlling pain.

The investigators also found that the increase in ACC activity caused by treatment with a painkiller was greatest in patients who had a vigorous response to placebo.

"The experience of pain is always subjective," Ingvar said. He and his colleagues point out that the placebo effect is influenced by several factors including a person's expectations of the treatment and desire to feel better. The research, by showing that placebo and a real painkiller activate the same brain regions, suggests that some of these same factors may be involved in triggering the pain relief of real medications, according to the report.

Despite the evidence that placebo can affect the brain, Ingvar said that the report "does not support the use of placebo alone in treatment." The findings do show, however, that the placebo effect "is part of every treatment," he said.

SOURCE: Sciencexpress 2002;10.1126.