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Sep 22 2009

The placebo effect

In the previous post, I described the practice of homeopathy and explained why it should no longer be taken seriously. Now that we know that its originator Samuel Hahnemann was basically treating his patients with water, what made him think his treatment was effective? There is no evidence that he was a fraud or charlatan, foisting on his patients something he knew was bogus in order to take their money. He was probably genuine in his belief in the efficacy of his treatment.

It is likely that he was misled by the placebo effect, where patients recover from an illness due to any number of factors that have nothing to do with treatment provided by the doctor. People who want to believe seize on these random events and see patterns that don’t exist. For example, since colds get better after a few days, it is possible to get gullible people to believe that practically anything is a cure for cold since if you take it soon after the onset of symptoms, presto, the cold disappears in a couple of days.

Steve Silberman in Wired Magazine describes how the placebo effect was discovered.

The roots of the placebo problem can be traced to a lie told by an Army nurse during World War II as Allied forces stormed the beaches of southern Italy. The nurse was assisting an anesthetist named Henry Beecher, who was tending to US troops under heavy German bombardment. When the morphine supply ran low, the nurse assured a wounded soldier that he was getting a shot of potent painkiller, though her syringe contained only salt water. Amazingly, the bogus injection relieved the soldier’s agony and prevented the onset of shock.

Returning to his post at Harvard after the war, Beecher became one of the nation’s leading medical reformers. Inspired by the nurse’s healing act of deception, he launched a crusade to promote a method of testing new medicines to find out whether they were truly effective.

In a 1955 paper titled “The Powerful Placebo,” published in The Journal of the American Medical Association, Beecher described how the placebo effect had undermined the results of more than a dozen trials by causing improvement that was mistakenly attributed to the drugs being tested. He demonstrated that trial volunteers who got real medication were also subject to placebo effects; the act of taking a pill was itself somehow therapeutic, boosting the curative power of the medicine. Only by subtracting the improvement in a placebo control group could the actual value of the drug be calculated.

The placebo explains why so many medical procedures that are now viewed with horror were standard treatments in the past. Bloodletting, bleeding with leeches, attaching maggots, dousing with cold water, were among the treatments once recommended. Charles Darwin suffered from all manner of undiagnosed ailments that included frequent vomiting and he subjected himself to various uncomfortable water treatments in the belief that they helped him. His beloved daughter Annie died of an unknown illness after receiving similar water treatments.

In my own building on the third floor is a small museum of medical history that contains all manner of gruesome-looking medical devices that no one thinks of using today but once were believed to be effective, even state-of-the-art. As long as the physician and patient had confidence in the treatment, it must have seemed to work.

Because of the repeated discrediting of medical treatments that were once considered effective, it has been suggested that the history of medicine is actually the history of the placebo effect, with new placebos replacing the old, leading to the uncomfortable suggestion that our current treatments, however sophisticated they may seem, are merely the latest placebos.

But there is reason to think that we now have a much better idea of what really works and what is a placebo because Beecher’s work led to the invention of the practice of double-blind experimental testing, where neither the patient nor the researcher collecting the data and doing the analyses knows who is receiving the experimental treatment and who is receiving the placebo.

By 1962, the government had started requiring drug companies to perform clinical tests with placebos in order to get approval and this has led to the elimination of outright quackery in medicine. Without such precautions, people can, even with the best of intentions, subtly distort the results to get the result they want or expect.

As a result of the widespread adoption of double-blind testing, there is good reason to think that our current practices are significantly better than those of the past, and that we are no longer so easily fooled by placebos.

Next: Using placebos as part of treatment.

POST SCRIPT: How double blind tests work

Double-blind tests are useful not only in medicine. Richard Dawkins shows what happens when it is used to test the claims of people who think they can detect the presence of water by dowsing.

It is interesting that when the tests show the dowsers that the “powers” they thought they had is non-existent, they make up stuff to enable them to continue believing. Does that remind you of anything?

1 comment

  1. 1
    disgruntled goat

    placebos are great. i have two in my coffee every morning.

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