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Acupuncture, Pain, And The Placebo Response
Expectation of pain relief is a powerful influence as studies continue to demonstrate. Positron-emission tomography (PET) scans and functional MRI imaging (fMRI) have provided modern tools to track the pain response and the effect of factors that modulate pain. Painful stimuli, transmitted to the brain via the spinothalamic tract, do indeed produce measurable increased activity in the thalamus, anterior cingulated, and somatosensory cortices.1-4 Effective pain modulating interventions show both attenuation of this activity as well as activation of alternate modulatory pathways in the rostral anterior cingulated and orbitofrontal cortices.1-4 There is also measurable increased activity in areas of the pons and midbrain that correspond with known pain modulating circuits such as the periaqueductal gray (PAG) and rostral ventromedial medulla (RVM).2,3 These effects are observed with the administration of opioid analgesics, effective acupuncture treatment, and in individuals termed "high-effect" placebo responders. All are reversed by administration of naloxone which, interestingly, does not increase pain in non-responders.2
To take offense that acupuncture may be viewed as "placebo response" would seem premature. With ongoing placebo research in conventional allopathic medicine, it appears that the mind-body disconnect is being bridged. Physical-chemical effects are being quantified by interventions that were once considered merely "psychological." The placebo response is so powerful, it has been proposed in pain research that a truly non-intervention group needs to be included rather than using a placebo-administered group as a control - in order to measure the effect of no treatment. Perhaps this is why studies utilizing sham acupuncture, either via use of non-meridian points or special non-penetrating needles, often fail to show a significant incremental effect of "true" acupuncture. Both are producing neurophysiological effects and the incremental improvement with acupuncture is difficult to discern.
We continue to employ a powerful tool that has been demonstrated to affect pain-modulating pathways. Oriental Medicine has always recognized the interconnectedness of mind and body. Distinctions between the two seem contrived in perception of the whole person. The concept that placebo is equivalent to no-effect has become dated. Perhaps a new term needs to be developed – expectation of healing, or treatment effect, for instance.
I propose that acupuncture used in the treatment of pain acts synergistically with this "placebo effect," amplifying or intensifying it – perhaps making "placebo responders" out of those who would not otherwise be. It is truly a privilege to have a tool at our disposal that helps to connect to the core of human functioning in order to promote fundamental healing.
For many of us, the need to objectively quantify the effects of acupuncture interventions is superfluous - if healing occurs, that is all that matters. For others, however, the presence of powerful imaging techniques and methodologies provides the promise of further documentation of that which we already know from experience.
- Michael A. Santoro, MD, MPH, FACPM, DABMA
Guest Editor
REFERENCES
- Cho Z-H, et al. fMRI Neurophysiological evidence of acupuncture mechanisms. Medical Acupuncture. 2003;14:16-22.
- Hoffman GA, Harrington A, Fields HL. Pain and the placebo – what we have learned. Perspect Biol Med. 2005;48(2);248-265.
- Love R. The placebo effect: is it all in the mind? Lancet Neurol. 2004;3(4):200.
- Zubieta JK, Bueller JA, Jackson LR, et al. Placebo effects mediated by endogenous opioid activity on mu-opioid receptors. J Neurosci. 2005;25(34):7754-62.
GUEST EDITOR INFORMATION
Dr Michael Santoro practices Occupational and Environmental Medicine and Medical Acupuncture at Midwest Health Strategies in Muncie, Indiana.
Michael A Santoro, MD, MPH, FACPM, DABMA*
3813 So Madison St
Muncie, IN 47302-5758
Phone: 765-751-3300 • Fax: 765-751-3351 • E-mail: msantoro@chsmail.org
*Correspondence and reprint requests
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