Western scientists first became seriously interested in researching the effects of acupuncture in the 1970s. Many of the early studies were poorly designed, and the results were often not reproducible. They were not sufficiently randomized or blinded, and placebo controls were unreliable or nonexistent. To date, no single theory has been put forth that can explain all the phenomena associated with acupuncture treatment.
In 1991, the World Health Organization proposed a standard nomenclature for the 400 acupuncture points and the 20 meridians connecting those points.12 The precise anatomical locations of these areas have not yet been identified definitively. They have a low electrical resistance compared with surrounding tissue. Theories attempting to correlate the acupuncture points with neurovascular bundles have been postulated but remain unproved. The existence of acupuncture points has been verified with galvanometer scanning. These devices measure electrical conductance and emit an audio signal when an area of low resistance is encountered. New points have been added and the location of some of the original ones redefined by this technique.
In some of the earliest research conducted, French acupuncturists Niboyet and Grall mapped many of the points.13,14 Darras attempted to prove the existence of the meridians by tracing the flow of the radionuclide technetium TC 99m sulfur colloid after it was injected into them.15 No published reports in the English-language medical literature have reliably confirmed scientific studies documenting either the existence or location of the meridians.16
The neurohumoral theory postulates that the analgesic effects of acupuncture are related to the release of neurotransmitters such as endogenous opioids. In addition, acupuncture appears to inhibit the transmission of C-fiber pain at the level of the spinal cord.17,18 Other physiological phenomena have also been observed with acupuncture by needling. They include vasodilation, increased serum cortisol, variations in serum glucose and cholesterol levels, increased white blood cell counts, and acid suppression.5 Their significance continues to be questioned.
Evidence-Based Approach
Many studies of acupuncture have methodological flaws. The biggest problem as yet unresolved is an appropriate placebo control.19 Sham acupuncture, which involves needling non-acupuncture points, is frequently the control of choice but has serious limitations.
In 1997, the landmark NIH consensus statement was probably the most important presentation of evidence supporting the efficacy of acupuncture.20 Conclusions made about the effectiveness of acupuncture were based on evidence from reliable studies. Many promising results emerged. Specific indications for use of acupuncture were identified on the basis of published reports of its effectiveness. Efficacy in treating dental pain and post-operative and chemotherapy-induced nausea were demonstrated. Research suggested its usefulness as an adjunct or alternative treatment for lower-back pain, osteoarthritis, addiction, and stroke rehabilitation. The panel also concluded that further research would likely uncover additional uses for acupuncture.
From the standpoint of acupuncture’s effectiveness, it can clearly benefit specific patient groups. It is most commonly used as a treatment for back pain.21 Since the NIH conference, further research has confirmed its effectiveness in treating a variety of medical conditions. (See Table 1, above)
Much of the ongoing research on acupuncture has focused on the use of functional magnetic resonance imaging of the brain, specifically on the areas that light up, or show brain activity, during activities or a state of pain.22-24 Acupuncture has been found to reduce the intensity of signals in such areas. The mechanism for the analgesic effects of acupuncture may be the result of reduced blood flow to the brain.24 Several studies have identified specific areas of the brain affected by pressure on various acupuncture points.25