Research Article: Phantom Acupuncture: Dissociating Somatosensory and Cognitive/Affective Components of Acupuncture Stimulation with a Novel Form of Placebo Acupuncture

Date Published: August 7, 2014

Publisher: Public Library of Science

Author(s): Jeungchan Lee, Vitaly Napadow, Jieun Kim, Seunggi Lee, Woojin Choi, Ted J. Kaptchuk, Kyungmo Park, Xi Luo.


In a clinical setting, acupuncture treatment consists of multiple components including somatosensory stimulation, treatment context, and attention to needle-based procedures. In order to dissociate somatosensory versus contextual and attentional aspects of acupuncture, we devised a novel form of placebo acupuncture, a visual manipulation dubbed phantom acupuncture, which reproduces the acupuncture needling ritual without somatosensory tactile stimulation. Subjects (N = 20) received both real (REAL) and phantom (PHNT) acupuncture. Subjects were retrospectively classified into two groups based on PHNT credibility (PHNTc, who found phantom acupuncture credible; and PHNTnc, who did not). Autonomic and psychophysical responses were monitored. We found that PHNT can be delivered in a credible manner. Acupuncture needling, a complex, ritualistic somatosensory intervention, induces sympathetic activation (phasic skin conductance [SC] response), which may be specific to the somatosensory component of acupuncture. In contrast, contextual effects, such as needling credibility, are instead associated with a shift toward relative cardiovagal activation (decreased heart rate) during needling and sympathetic inhibition (decreased SC) and parasympathetic activation (decreased pupil size) following acupuncture needling. Visual stimulation characterizing the needling ritual is an important factor for phasic autonomic responses to acupuncture and may undelie the needling orienting response. Our study suggests that phantom acupuncture can be a viable sham control for acupuncture as it completely excludes the somatosensory component of real needling while maintaining the credibility of the acupuncture treatment context in many subjects.

Partial Text

While acupuncture has been shown to reduce pain in many previous clinical trials, statistically significant differences between real and sham acupuncture have not been consistently demonstrated [1], [2], [3], [4]. This may be due to the fact that sham acupuncture commonly has included a somatosensory or tactile component. In fact, previous studies have not separated the complex acupuncture ritual into its constituent components, which could better determine the specific effects of this therapeutic intervention [1]. In this study, we propose an experimental design that allows for a separation of the acupuncture ritual into a somatosensory and contextual component, with autonomic outflow and psychophysical outcome metrics.

All research procedures were approved by the Institutional Review Board (IRB) committee of Sangji University (IRB approval number: SJ 2007-071201), and investigations were conducted in accordance with the principles of the Declaration of Helsinki. All participants in the study provided written informed consent.

For the 20 subjects, order of REAL or PHNT session was pseudo-randomized such that 10 received real acupuncture first, while the rest received phantom acupuncture first. There was no significant difference in age (REAL first: 21.1±2.9 years old, PHNT first: 22.5±2.3 years old; mean±STD), handedness (REAL first: 73.4±28.9%, PHNT first: 68.3±54.7%; 100%: right handed, −100%: left handed), positive expectation about acupuncture efficacy (REAL first: 2.4±0.2, PHNT first: 2.3±0.5; out of 1 to 5 range) or state/trait anxiety (STAI-state: REAL first: 27.8±7.5, PHNT first: 26.8±5.6; STAI-trait: REAL first: 33.7±5.2, PHNT first: 31.8±8.3) between the two order groups. From retrospective credibility questionnaires, we classified our subjects into PHNTc (PHNT credible; who reported high needling credibility for PHNT, n = 11) and PHNTnc (PHNT non-credible; who reported low needling credibility, n = 9).

In this study, we have developed and tested a new form of placebo acupuncture, referred to as phantom acupuncture, which was characterized by an acupuncture needling intervention induced solely by visual display. We applied real (REAL) and phantom (PHNT) acupuncture and retrospectively re-classified subjects into two groups based on PHNT credibility (PHNTc, who found phantom acupuncture credible, n = 11; and PHNTnc, who did not find phantom acupuncture credible, n = 9). Physiological responses to REAL and PHNT were measured via autonomic response (heart rate, skin conductance, pupil size), while psychophysical responses were assessed by subjective ratings of needle sensation (Table 1). Real acupuncture induced greater skin conductance response, suggesting that the somatosensory component of acupuncture underlies the sympathetic outflow produced by acupuncture needle stimulation. We found that both real and phantom acupuncture (when credible) induced notable acupuncture sensation. The credibility of the ritual, a contextual component of acupuncture, was important for inducing robust deqi sensation, but was less important for autonomic response to purely visual phantom acupuncture, suggesting that some stimulus-associated autonomic response may be the result of sub-conscious processing that does not play a role in conscious cognitive re-evaluation of a ritual as credible or not.