Not all placebos are equivalent in their effects, scientists have discovered from a study of sham acupuncture vs an oral inert pill to treat pain. The research is the first to investigate how the placebo effect varies in specific clinical environments (Kaptchuk TJ et al. BMJ. doi:10.1136/bmj.38726.603310.55 [published online ahead of print February 2, 2006]).
The study of 270 individuals with chronic arm pain due to repetitive use included two phases. First, half of the patients were given sham acupuncture and half were given a placebo pill for 2 weeks. Pain decreased to a similar extent in both groups. Next, participants were randomized to continue their placebo treatment or to begin active treatment of the same type: half of the patients were randomized to sham vs real acupuncture twice a week for 4 weeks, and half were randomized to placebo pill vs amitriptyline once daily for 6 weeks. Patients receiving sham acupuncture reported a more significant decrease in pain and symptom severity than did those receiving a placebo pill. At 2 weeks, 75% of participants in the acupuncture group believed they were receiving active treatment compared with 48% in the pill group, a difference that continued to the end of the study. However, differences between the two groups were not significant in objective measures such as arm function and grip strength.
Hampton T. Not All Placebos Are Equal. JAMA. 2006;295(10):1111. doi:10.1001/jama.295.10.1111