Scans show placebo acts on brain's pain center

[Guest guest]

Scans show placebo acts on brain's pain center

By Merritt McKinney

NEW YORK, Feb 07 (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. 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.