2 February 2006
Ritual A Critical Element Of Placebo Effect
by Kate Melville
The nature of the so-called placebo effect continues to tantalize scientists as an increasing number of lab experiments are detecting robust physiological responses to placebos. And just to add fuel to the fire, a new study, published in the British Medical Journal, takes placebo investigations one step further by comparing the effects from two different placebo treatments.
The researchers, from Harvard Medical School, usually use placebos in clinical trials to test the effectiveness of a new treatment, but this is the first study that pitted one placebo against another. Such an experiment may seem wrong-headed and researcher Ted Kaptchuk admits that "it's upside down research." The two placebos that Kaptchuk looked at were a sham acupuncture device and an inert pill.
The study, involving over 250 subjects with chronic arm pain, was conducted in two phases. In the first phase, half were given sham acupuncture, and half were given a placebo pill over a two week period. The findings from this phase showed no strong evidence for an enhanced effect with placebo acupuncture compared to placebo pills.
But in the second phase of the study, the results were more interesting. This phase saw half the patients entered in a sham acupuncture device versus real acupuncture trial, and the other half in a placebo pill versus real pain pill trial. Both trials in this phase were conducted over a longer period.
The results indicated that the 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 researchers say that this shows 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."
While the results are based on subjective reports from patients about their perception of pain and the severity of their condition, Kaptchuk says the results of this study add evidence pointing to the existence of a placebo effect in a clinical environment.
He also believes that the results provide evidence that what doctors tell patients about side effects directly influences their experience of them. Prior to participating in the study, the researchers 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 though the bogus treatments could not possibly cause them.
Source: Harvard Medical School