NCPA - National Center for Policy Analysis

The Placebo Effect Is Real

April 2, 2001

Simply participating in a medical-research trial sometimes improves a person's health. In what are called "double-blind" studies, investigators use placebos, or dummy treatments, and both participants and staff are unaware of who is receiving an active treatment. Yet anywhere from 10 percent to 100 percent of the people taking placebos report improvement.

  • Studies indicate problems like pain and depression respond particularly well to placebos.
  • Blood pressure, cholesterol and heart rate are also affected by placebos, as are warts.
  • On average, about a third of people taking placebos report a benefit. A drug is considered beneficial only if it can beat the placebo; but researchers have become increasingly interested in why placebos work at all.

Psychology accounts for a lot of the "placebo effect." For example, people receiving a placebo they're told is morphine report more pain relief than people given placebos masquerading as aspirin. Likewise, placebos people think are brand-name aspirin reduce headache pain more than placebos disguised as generic aspirin.

People's perceptions of their treatment also play an important role in healing. Among the studies comparing active treatment with both placebo treatment and no treatment at all, most have shown a group receiving a placebo is likely to improve faster than an untreated group.

  • Some of the improvement may be spontaneous and reflect random fluctuations in their disease symptoms.
  • People are more likely to report positive results because they think that's what the researchers want to hear.
  • And people getting placebos still receive counseling about their disease and other care.

Fabrizio Benedetti of the University of Torino found that people's responses to placebos can be blocked by an antinarcotic drug called naloxone. It blocks the effect of both narcotics and natural painkillers released by the brain.

Researchers say this is "incontrovertible physical evidence" of a placebo effect.

Source: Damaris Christensen, "Medicinal Mimicry: Sometimes, placebos work -- but how?" Science News, February 3, 2001.


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