June 25, 2009


The Placebo Effect (Harriet Hall, 5/20/09, MD, Skeptic)

In a study of pain after dental surgery, patients were given either intravenous morphine or a saline placebo. If they were told that the saline was a powerful new painkiller, they got just as much relief as the patients who received morphine. In another study, all patients were given morphine for post-op pain, but only half were told they were getting it. The patients who didn’t know they were getting it only experienced half as much pain relief. In a study of acupuncture for post-op dental pain, there was no difference between the “real” acupuncture and placebo “sham” acupuncture groups, but when they asked patients which group they thought they were in, they discovered that those who believed they were in the “real” group reported significantly more pain relief than those who believed they were in the “sham” group — regardless of which group they were actually in!

We not only know placebos “work,” we know there is a hierarchy of effectiveness:

* Placebo surgery works better than placebo injections
* Placebo injections work better than placebo pills
* Sham acupuncture treatment works better than a placebo pill
* Capsules work better than tablets
* Big pills work better than small
* The more doses a day, the better
* The more expensive, the better
* The color of the pill makes a difference
* Telling the patient, “This will relieve your pain” works better than saying “This might help.”

In one study patients were given the same aspirin in either a brand name bottle or an unlabelled bottle; it worked better if it was labeled as a brand they recognized. Our pharmacy used to stock two different brands of allergy pills that were made in the same factory and were identical except that one was green and the other was blue. When a patient said it wasn’t working any more, we’d switch him to the other brand and it would start working again.

Along with placebo effects, there are nocebo (“I harm”) effects. People getting inert treatments often report new symptoms. A friend of mine stopped taking her homeopathic sleep remedy because she thought it was causing side effects. (Homeopathy is the ultimate placebo because its remedies usually contain nothing but water.) In the Women’s Health Initiative study of postmenopausal hormone treatment, when the treatment was stopped, 63% of the women taking hormones reported withdrawal symptoms, but so did 40% of the women taking a placebo. If we tell patients a treatment may cause nausea, they are far more likely to report nausea than if we don’t mention that possibility.

The placebo effect is mainly subjective. Placebos don’t work on patients who are asleep or unconscious. You have to know you’re being treated. Placebos don’t keep women from getting pregnant. They don’t cure cancer, heal broken bones, or do anything you can measure objectively. They work for more elusive complaints like headache, depression, itching, shortness of breath, tension, indigestion, and other symptoms that require us to accept the patient’s self-report of what he is experiencing.

Hygiene, nutrition and inoculations--the rest is bunk.

Posted by Orrin Judd at June 25, 2009 9:24 AM
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