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.