I think I am not in pain therefore I am not in pain

Doctors who assure patients that treatments will cure them have the right idea. Truth? Truth? What is truth?

By Owen Dyer

The placebo effect may be all in the mind, but the changes it works are real, physical and measurable, according to two parallel studies whose combined results were published in the February 20 issue of Science. The work was done at the Ann Arbor Veterans Affairs Health Care System, University of Michigan and Princeton University.

Researchers used functional magnetic resonance imaging (fMRI) to map changes in blood flow in the brains of volunteers who were subjected to electric shocks or heat. They were given a topical cream first, and were falsely told that it was an anti-pain cream. They reported less pain when the cream had been applied -- a typical case of placebo effect -- but more importantly, the MRI scan revealed that the parts of the brain that normally register extra activity under pain stimulus were unusually quiescent when the placebo cream was applied.

The placebo effect appears to be a case of the higher, conscious brain commanding the lower brain. Expectation of relief begins, naturally enough, in the prefrontal cortex. Shortly after this burst of brain activity, the MRI revealed a falling-off of activity in the brain regions that carry pain signals: the thalamus, somatosensory cortex, and other parts of the cerebral cortex.

"We've shown what the old family doctor knew very well -- that his interaction with the patient made a great difference in the effectiveness of whatever treatment he was giving, " said one of the researchers, Dr Kenneth Casey, who has studied pain for three decades. Dr Casey is a consultant neurologist for Veterans Affairs and a professor at the University of Michigan.

"If you're providing a treatment to a patient, it's important that you realistically provide them with the expectation that it would work, so you enhance the effect, " said Dr Casey. "If you gave them a drug or any kind of treatment with the attitude, either explicit or implicit, that this might not be effective, it would be much less likely to be effective. "

He is optimistic that further research into the neural pathways of the placebo response could yield new pain treatments, if nothing else. "One could imagine compounds that would activate these control systems specifically, " he said. Unfortunately such compounds could raise consent issues, since they would presumably only work if the doctor lied to the patient about what they were really for.