All placebos not created equal

While researchers usually use placebos in clinical trials to test the effectiveness of a new treatment, a trial reported in the Feb. 1, 2006 British Medical Journal pitted one placebo against another.

“It’s upside down research,” said Ted Kaptchuk, assistant professor of medicine and associate director of the Division for Research and Education in Complementary and Integrative Medical Therapies and the Osher Institute at Harvard Medical School. “We investigated whether a sham acupuncture device has a greater placebo effect than an inert pill.”

The study of 270 individuals with chronic arm pain had two phases. In the first phase, 135 patients were given sham acupuncture, and another 135 patients were given a placebo pill for two weeks. During this period, investigators found no strong evidence for an enhanced effect with placebo devices compared with placebo pills.

In the second phase of the study, the same patients were randomized again, with half the patients entered in a sham acupuncture device versus real acupuncture trial, and the other half in a placebo pill vs. real pain pill trial. The acupuncture trial extended four more weeks (the length believed needed to see improvement), and the pill trial lasted six more weeks (the length needed to have the real drug in the bloodstream).

In the second phase of the study, patients receiving sham acupuncture reported a more significant decrease in pain and symptom severity than those receiving placebo pills for the duration of the trials. The results of this study show that the placebo effect varies by type of placebo used.

“These findings suggest that the medical ritual of a device can deliver an enhanced placebo effect beyond that of a placebo pill. There are many conditions in which ritual is irrelevant when compared with drugs, such as in treatment of a bacterial infection,” said Kaptchuk, “but the other extreme may also be true. In some cases, the ritual may be the critical component.”

The enhanced placebo effect illustrated in this study applied only to subjective reports from patients about their perception of pain and the severity of their condition. More objective measures of grip strength showed no difference in improvements between the two placebos.

The results also provided evidence that what doctors tell patients about side effects directly influences their experience of them. Prior to participating in the study, doctors provided informed consent forms alerting the patients as to the side effects they might experience: temporary soreness for acupuncture and fatigue and dry-mouth for the pills. Of those receiving placebos, 25 percent of sham acupuncture and 31 percent of placebo pill patients reported experiencing the very side effects suggested to them even when nothing was administered to cause them.

This study takes the first step away from examining the placebo effect as a generalized phenomenon to one investigating how it varies in specific clinical environments.