May 21, 2009


Hooked on a Feeling: This is your brain on a placebo. (Sharon Begley, Jun 1, 2009, NEWSWEEK)

As far as the body is concerned, a placebo is nothing—a sugar pill, a sham treatment, an inert compound. But try telling that to the brain, as scientists led by Daniel Cherkin of Group Health Center for Health Studies in Seattle recently saw. They assigned 638 adults with chronic lower-back pain to receive either standard acupuncture therapy, customized acupuncture (tailored to the individual, such as by using nonstandard acupuncture points), sham acupuncture (toothpicks in acupuncture-needle guide tubes that mimic the feel of real acupuncture) or standard back-pain care, such as anti-inflammatory drugs and massage. As the scientists reported this month in Archives of Internal Medicine, pain diminished significantly for 60 percent of the people in all three acupuncture groups—but for just 39 percent of patients receiving usual care. On average, both fake and real acupuncture reduced pain more than twice as much as standard care. Weirdly, this is being spun as "acupuncture is better than standard medical care for back pain!" I say "weirdly" because the key finding is that sham acupuncture delivered as much benefit as real acupuncture. And the most parsimonious explanation for that finding is inescapable: it is possible to think yourself out of pain.

In fact, the power of thought to relieve pain has been known since 1978, when neuroscientists began studying placebo responses in earnest. Now they have even mapped the brain processes that underlie it. When people expect their pain to diminish, typically because a doctor tells them that a little pill or other treatment will do so, that mere expectation produces activity in the prefrontal cortex, site of higher mental function, which in turn activates other regions to release the brain's own homemade opioids, says Fabrizio Benedetti of the University of Turin Medical School, a pioneer in placebo research. (A big advance in understanding placebo was showing that a drug that blocks the effects of opioids also blocks the placebo effect on pain, prima facie evidence that the brain's endogenous opioids are in play.) The higher the expectations, the greater the pain relief, too. When scientists led by Dan Ariely of Duke University gave volunteers identical dummy pills before and after an electric shock, and told some of their human guinea pigs that the pills were analgesics costing $2.50 and others that they cost 10 cents, more of those getting the expensive placebo than the cheaper one reported pain relief (85 percent vs. 60 percent). too embarrassing to be contemplated.

Posted by Orrin Judd at May 21, 2009 12:01 PM
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