Comparison of the placebo effect between different non-penetrating acupuncture devices and real acupuncture in healthy subjects: a randomized clinical trial

This randomized controlled trial investigated the efficacy of different placebo acupuncture methods for participant blinding in clinical trials. The research was conducted at the Federal University of Sergipe with 321 healthy volunteers, with no prior experience with acupuncture and no pain in the regions selected for application. Participants were randomized into 14 different groups, testing real acupuncture versus three distinct placebo methods: Park Sham device, adhesive foam needle technique, and insertion followed by immediate removal. Two acupuncture points were tested: ST-25 (abdominal region, 2 cun lateral to the umbilicus) and BL-52 (lumbar region, at the level of L2).

The study design was double-blind, with two investigators: one responsible for assessments (blinded to treatment) and another for application of the techniques. All procedures lasted 30 minutes, simulating a real acupuncture session. Participants were instructed not to observe the needles during the procedure. After treatment, questionnaires were administered to evaluate perception of the type of treatment received, discomfort intensity, location of sensation, and duration of effects.

The results demonstrated that there was no statistically significant difference between groups regarding the perception of the type of stimulation received. The percentage of participants who believed they had received real acupuncture ranged from 69.56% to 91.30% at the ST-25 point and from 69.56% to 86.95% at the BL-52 point, with no significant differences between methods. Discomfort intensity was low and similar across all groups (p = 0.768). The needling sensation was reported as localized at the application point by most participants in all groups, not diffuse.

Interestingly, the duration of sensation was significantly longer in the real acupuncture group at the BL-52 point compared to some placebo groups, suggesting that this parameter may be an indicator of needle penetration depth. The mixed groups, which combined real acupuncture on one side of the body with placebo on the other, also presented results similar to the other groups. The clinical implications of this study are important for acupuncture research methodology. The results indicate that any of the three placebo methods tested can be used in future clinical trials, since all demonstrated similar efficacy in blinding participants.

This provides researchers with greater flexibility in choosing the most appropriate placebo method for their specific experimental design. The study contributes significantly to resolving controversies over which placebo method is most appropriate, a fundamental issue that has impacted the quality and interpretation of acupuncture studies. The absence of differences in perception between real and placebo acupuncture also raises interesting questions about the mechanisms by which acupuncture produces its therapeutic effects, highlighting the importance of nonspecific treatment components.