Are Minimal, Superficial Or Sham Acupuncture Procedures Acceptable as Inert Placebo Controls?

Abstract

Most controlled trials of acupuncture have used minimal, superficial, sham, or ‘placebo’ acupuncture. It has recently been demonstrated that light touch of the skin stimulates mechanoreceptors coupled to slow conducting unmyelinated (C) afferents resulting in activity in the insular region, but not in the somatosensory cortex. Activity in these C tactile afferents has been suggested to induce a ‘limbic touch’ response resulting in emotional and hormonal reactions. It is likely that, in many acupuncture studies, control procedures that are meant to be inert are in fact activating these C tactile afferents and consequently result in the alleviation of the affective component of pain. This could explain why control interventions are equally effective as acupuncture in alleviating pain conditions that are predominantly associated with affective components such as migraine or low back pain, but not those with a more pronounced sensory component, such as osteoarthritis of the knee or lateral epicondylalgia.

Acupuncture for primary dysmenorrhoea: a systematic review

“…67 Currently, some papers have suggested that sham acupuncture may not be inert. 68,69 Superficial needling was found to be superior to the placebo diazepam. 70 It will be necessary to re-examine trials of acupuncture in which the sham was assumed to be inert, but was not inert.…”

Imperfect placebos are common in low back pain trials: a systematic review of the literature

“…For example, among non-pharmaceutical trials, we found that indistinguishability was more frequent for trials of acupuncture but all these indistinguishable placebos consisted of potentially genuine treatments. In acupuncture trials, the use of invasive sham acupuncture techniques has been criticised because the mechanism behind the effects of acupuncture may not depend on the depth or location of needling, but on needling itself [98,144]. Accordingly, the lack of a clear understanding on the mechanisms underlying specific therapeutic effects is also a challenge to the design of indistinguishable placebos in other complex interventions [66].…”

Complementary and alternative medicine therapies for the anesthesiologist and pain practitioner: a narrative review

“…Furthermore, even a light touch can illicit changes in the limbic system, making it difficult to design a true control for physical modalities. 73 Despite controversy over a lack of adequate blinding and potential intellectual biases against acupuncture and other complementary therapies, evidence exists to support these therapies even at the mechanistic level. 14,[74][75][76] For example, several animal models have shown a therapeutic effect for acupuncture and other CAM therapies.…”

“…Furthermore, since animals likely do not understand the difference between true vs sham therapies, we can infer that they are not likely to exhibit a placebo response. [71][72][73][74][75][76][77][78][79][80][81] Some argue that acupuncture is no better than placebo since a few human studies showed no significant difference between sham needling and true acupuncture-ignoring the effects of needle insertion itself. 82 Nevertheless, blinding attempts with non-penetrating shams are possible in humans.…”