Sham device v inert pill: randomised controlled trial of two placebo treatments.
Level 2 - randomized trial
Individual randomized controlled trial comparing two placebo modalities.
PubMed 16452103 · doi:10.1136/bmj.38726.603310.55
What was done
Researchers evaluated whether a sham device produced a greater placebo effect than an inert pill in 270 adults with persistent repetitive-use arm pain (duration ≥3 months, pain score ≥3 on a 10-point scale). The study analyzed the 2-week placebo run-in period from two nested trials (evaluating acupuncture and amitriptyline against their respective placebos) and tracked patients continuing on placebo. Participants received either sham acupuncture twice weekly for 6 weeks or a placebo pill once daily for 8 weeks. Primary outcome was arm pain on a 10-point scale; secondary outcomes included symptom severity (Levine scale), upper extremity function (Pransky scale), and grip strength.
What was found
During the initial 2-week run-in, pain decreased in both groups without a significant between-group difference (-0.14, 95% CI -0.52 to 0.25, P = 0.49). Arm function improved more with the placebo pill during run-in (2.0, 95% CI 0.06 to 3.92, P = 0.04), while symptom severity and grip strength did not differ. Across the full longitudinal treatment period, the sham device group experienced a significantly greater weekly reduction in arm pain than the pill group (-0.33 [95% CI -0.40 to -0.26] vs -0.15 [95% CI -0.21 to -0.09], P = 0.0001) and greater weekly reduction in symptom severity (-0.07 [95% CI -0.09 to -0.05] vs -0.05 [95% CI -0.06 to -0.03], P = 0.02). Differences were not significant on the function scale or for grip strength. Reported adverse effects differed between the two groups.
Why it matters
This trial provides direct empirical evidence that the magnitude of a placebo response is malleable and varies according to the therapeutic ritual, with a sham physical procedure eliciting stronger subjective analgesia than an oral pill.
Limits
The trial was single-blind and primarily demonstrated differences on subjective self-report scales rather than objective measures like grip strength. Treatment regimens differed in contact frequency and overall duration (twice-weekly visits for 6 weeks versus daily pill-taking for 8 weeks), which may confound the modality comparison. Data originated from nested run-in periods of trials assessing specific active treatments (acupuncture and amitriptyline), potentially introducing distinct baseline treatment expectations.
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- supports The strength of a placebo response increases with the size and invasiveness of the intervention, with larger pills producing stronger effects than smaller pills, and sham injections producing stronger effects than pills.