Is Sham Laser a Valid Control for Acupuncture Trials?

This methodologic study investigated whether sham (placebo) laser can serve as a valid control in laser-acupuncture and needle-acupuncture research. The work was motivated by the need to find adequate placebo controls for acupuncture studies, one of the greatest methodologic challenges in this area.

The researchers conducted a double-blind crossover study in 34 healthy volunteers at the University of Munich, Germany. Each participant received both active laser and sham laser treatment, in sessions separated by 3-4 days. The active laser used 830 nm infrared radiation at 22-23 mW, applied for 45 seconds at each acupuncture point (LI-4, LU-7, and LR-3). The sham laser kept only the visible red LED light, with no therapeutic laser emission.

The primary objective was to determine whether participants could distinguish between the two treatments. Results showed that only 44% of volunteers correctly identified the active laser in the first session and 41% in the second — rates close to chance (50%), indicating that the treatments were indistinguishable. Surprisingly, 49% of participants reported 'deqi'-like sensations (the characteristic acupuncture sensation) with the sham laser, compared with 46% with the active laser, without statistical difference.

The intensity of perceived sensations was also similar between groups: 2.34 points on the visual analog scale (0-10) for the active laser versus 2.49 for the sham laser. Interestingly, volunteers with prior experience with acupuncture reported more intense sensations but were no better at identifying the active treatment.

The researchers also analyzed credibility data from three prior studies, comparing sham laser with needle acupuncture in 186 patients. Results showed that the credibility of sham laser was equivalent to that of traditional acupuncture, strengthening its potential as a placebo control.

The clinical implications are significant. This study demonstrates that sham laser can serve as a valid placebo control both for laser-acupuncture studies and for needle-acupuncture studies. Unlike other placebo controls (such as superficial needling), sham laser does not produce peripheral sensory stimulation, enabling specific assessment of the effects of needling versus non-specific effects.

A crucial advantage of sham laser is that it allows blinding of both patient and therapist, something difficult to achieve with placebo needles. This represents an important methodologic advance, since many acupuncture studies are criticized for the impossibility of adequately blinding the therapists.

The study also revealed that substantial placebo effects can occur even without peripheral sensory stimulation, suggesting that psychological and contextual factors (such as attention, relaxation, and expectations) play an important role in the effects of acupuncture.

Limitations include the use of red light in the sham device, which theoretically could have its own therapeutic effects, though the low power (20 μW) and short application time make this unlikely. Another limitation is that technical devices may be perceived differently from manual techniques by patients.

This work contributes significantly to acupuncture research methodology, offering a more rigorous placebo control tool that can improve the quality of future clinical trials in this area.