Science plumbs placebo effect

When an inert placebo acts like a drug, is it just a psychological illusion? Or is it a real biological effect? Research reported last week suggests that it's both. The mere belief that they had received a pain killer was enough to release the brain's natural painkilling endorphins in the patients tested, scientists say.

This opens a new line of research into the placebo puzzle. The effect has been demonstrated often enough to show that some patients appear to benefit from such belief. But there hasn't been enough evidence to convince skeptics that anything more than the so-called power of suggestion is at work. That's changing. "The findings of this study are counter to the common thought that the placebo effect is purely psychological due to suggestion and that it does not represent a real physical change." says University of Michigan neuroscientist Jon-Kar Zubieta. He is principal author of the study published Aug. 24 in The Journal of Neuroscience.

Some mind/body effects are well known. Adrenaline flows when firefighters go into action. The sight of a lion induces physical changes that prepare a zebra to flee. Humans often experience a similar fight-or-flight reaction to a perceived threat.

But it's been too much of a stretch for many neuroscientists to accept that belief in fake medication can produce medical benefits that can be objectively verified.

Some researchers have been closing in on such verification by using brain scans to search for telltale brain activity in placebo studies. Last year, Columbia University psychologist Tor D. Wager and colleagues reported that when patients felt pain relief from a placebo, activity decreased in the pain-sensitive areas of their brains. (Dr. Wager was at the University of Michigan at that time.)

But such proof by coincidence with brain-scan changes isn't strong enough to convince skeptics that mere belief affected the brain. The brain-activity changes could be unrelated to the mental state, they argue.

Reporting their work in Science, the research team pointed out that such circumstantial evidence has given plausibility to "the idea that sensory experience is shaped by one's attitudes and beliefs." They acknowledge that, while pain does have "sensory components," it is "a psychologically constructed experience."

In his book "The Anatomy of Hope," Harvard Medical School physician Jerome Groopman notes that "a change of mind-set can alter neurochemistry both in a laboratory setting and in the clinic." He says he found relief himself from persistent back pain in the hope inspired by an empathetic fellow physician. He explains that "belief and expectation - the key elements of hope - can block pain by releasing the brain's [pain killing] endorphins and enkephlins, mimicking the effects of morphine."

Dr. Zubieta's team explored this effect by giving seven patient volunteers salt solution injections while seven other patients received the real pain killer. The placebo recipients' sense of relief coincided with the release of actual pain-numbing brain chemicals. This is a much stronger indication of the placebo mind/body connection than the enigmatic changes observed in brain scans.