An estimated 39.4 million US adults suffer from persistent pain,1 and the National Institutes of Health indicate that pain affects more Americans than diabetes, heart disease, and cancer combined.2
As physicians, we know that conventional options to manage chronic pain leave much to be desired and that more evidence-based treatment options are sorely needed. Patients know this, too, and turn to complementary therapies for pain more than for any other diagnosis.3
Case in point: The use of acupuncture is growing. Its use in the United States tripled between 1997 and 2007.4 In addition, the research base for acupuncture is rapidly expanding. From 1991 to 2009, nearly 4000 acupuncture research studies were published, with studies on pain accounting for 41% of the acupuncture literature.4
But acupuncture is not without controversy. This is due to a lack of a universally accepted biologic mechanism, theories of use and efficacy based in an alternative medical system (traditional Chinese medicine [TCM]), and conflicting views of the evidence.
This article will help make sense of this growing body of knowledge by summarizing the latest evidence and addressing 7 common questions about acupuncture for pain conditions. Applying this information will give you the confidence to counsel patients appropriately and decide if acupuncture fits within their pain management plan.
1. What is acupuncture and how does it work?
Acupuncture, which has a 2000-year history of use, involves inserting needles at various points throughout the body to promote healing and improve function. Although acupuncture represents one piece of TCM (which is a holistic system that also includes herbal medicine, nutrition, meditation, and movement), it is often offered as an independent therapy.
Acupuncture point locations are determined either by using an underlying theoretical framework, such as TCM, or by using anatomic structures, such as muscular trigger points. Providers today often employ a hybrid approach when delivering acupuncture treatment. That is, practitioners may choose point locations based on TCM, but they may combine the practice with local treatments that are based on current knowledge of anatomy. For example, a patient presenting with low back pain may be treated utilizing traditional points located near the ankle and knee, and also by needling active trigger points in the quadratus lumborum muscle.
The mechanism of action. One of the reasons for the continuing controversy surrounding acupuncture is the lack of a clear understanding of its underlying mechanism of action. For centuries the “how” of acupuncture has been explained in poetic terms such as yin, yang, and qi. Only in the past half-century have we begun investigating the potential biologic mechanisms responsible for the physiologic effects seen with acupuncture treatment.
While research has uncovered several interesting theories, how these mechanisms interact to produce therapeutic effects is still unclear. However, looking at various components of the nervous system helps to provide some insight.
Consider the nervous system. One way to conceptualize the mechanisms of acupuncture is to consider the various levels of the nervous system and how each level is affected. In the central nervous system, needling an acupuncture point stimulates the natural endorphin system, altering the pain sensation.5 This effect is reversible with naloxone in animal models, indicating that blocking the endorphin system interferes with the analgesic benefits of acupuncture.5
Serotonergic systems are also involved centrally. Functional magnetic resonance imaging studies have shown that needling specific acupuncture points modulates areas of the brain.
In the spinal cord, the gate control theory is believed to play a role. (The gate control theory puts forth that nonpainful input closes the “gates” to painful input, which prevents pain sensations from traveling to the central nervous system.) Modulation of sensory input occurs at the level of the dorsal horn of the spinal cord during an acupuncture treatment, which can affect the physiologic pain response.6 Opioid receptors are also affected at the spinal cord level.7
Lastly, multiple chemicals released peripherally, including interleukins, substance P, and adenosine, appear to contribute to acupuncture’s analgesia.6 We know this because a local anesthetic injected around a peripheral nerve at an acupoint blocks the analgesic effect of acupuncture.8 Taken together, acupuncture treatment produces physiologic changes in the brain, spinal cord, and at the periphery, making it a truly unique therapeutic modality.
2. Is acupuncture an effective treatment for pain?
Yes, but before we look at the individual studies, it is important to mention some of the shortcomings of the research to date. First, acupuncture trials lack a standard sham control intervention. Some sham treatments involve skin penetration, while others do not. This has led to controversy regarding whether the sham interventions themselves are physiologically active, thus lessening the magnitude of effect for acupuncture. This is a point of contention in the acupuncture literature and a factor to consider when deciding if results have clinical significance.