Specifying the nonspecific components of acupuncture analgesia

Abstract

It is well known that acupuncture has pain-relieving effects, but the contribution of specific and especially nonspecific factors to acupuncture analgesia is less clear. One hundred one patients who developed pain of ≥ 3 on a visual analog scale (VAS, 0 to 10) after third molar surgery were randomized to receive active acupuncture, placebo acupuncture, or no treatment for 30 min with acupuncture needles with potential for double-blinding. Patients' perception of the treatment (active or placebo) and expected pain levels (VAS) were assessed before and halfway through the treatment. Looking at actual treatment allocation, there was no specific effect of active acupuncture (P=.240), but there was a large and significant nonspecific effect of placebo acupuncture (P<.001), which increased over time. Interestingly, however, looking at perceived treatment allocation, there was a significant effect of acupuncture (P<.001), indicating that patients who believed they received active acupuncture had significantly lower pain levels than those who believed they received placebo acupuncture. Expected pain levels accounted for significant and progressively larger amounts of the variance in pain ratings after both active and placebo acupuncture (up to 69.8%). This is the first study to show that under optimized blinding conditions, nonspecific factors such as patients' perception of and expectations toward treatment are central to the efficacy of acupuncture analgesia and that these factors may contribute to self-reinforcing effects in acupuncture treatment. To obtain an effect of acupuncture in clinical practice, it may therefore be important to incorporate and optimize these factors.

Keywords: Acupuncture analgesia; Expectation; Nonspecific; Perception; Placebo analgesia.

Fig. 1. Experimental design

Patients who developed pain levels of ≥3 (0–10) up to 4 h following surgical removal of 1 mandibular third molar were randomized to receive active acupuncture (AA), placebo acupuncture (PA), or no treatment (NT) for 30 min. Prior to the treatment (−2 min), halfway through the treatment (13 min), and at the end of the treatment (28 min), actual pain levels and expected pain levels for subsequent time points were measured. Needles were rotated at insertion, at 15 min, and at 30 min when they were removed.

Fig. 2. Active and placebo acupuncture needles as well as the acupuncture points

Each needle assembly comprises an opaque guide tube (1) and upper stuffing (2) to provide resistance to the needle body during its passage through the guide tube. The body of penetrating needle (3) is longer than the guide tube by an amount equal to the insertion depth, but the body of the non-penetrating needle (4) is only long enough to allow its blunt tip to press against the skin when the needle body is advanced to its limit. The non-penetrating needle contains stuffing at the bottom as well (5) to give a sensation similar to that of skin puncture and tissue penetration. Both needles have a stopper (6) that prevents the needle handle (7) from advancing further when the sharp tip of the penetrating needle (8) or the blunt tip of the non-penetrating needle (9) reaches the specified position. The pedestal (10) on each needle is adhesive, allowing it to adhere firmly to the skin surface. The diameter of the needles used in this study was 0.16 mm.

Fig. 3. Comparisons of treatment groups

Comparison of pain intensity and pain unpleasantness in active acupuncture, placebo acupuncture and no treatment groups during the 30 min of treatment. Data are shown for both actual and perceived treatment allocation.