Abstract Pain is one of the most prevalent conditions for which patients seek medical attention. Additionally, the number of patients who utilize complementary and alternative medicine as a treatment of pain either in lieu of, or concurrent with, standard conventional treatments continues to grow. While research into the mechanisms, side effect profiles, and efficacies of these alternative therapies has increased in recent years, much more remains unknown and untested. Herein, we review the literature on complementary and alternative medicine for pain, with particular emphasis on evidence-based assessments pertinent to the most common alternative therapies, including acupuncture, herbal therapy, massage therapy, hypnosis, tai chi, and biofeedback.
Keywords Complementary medicine • Alternative medicine • Holistic • Mind-Body • Pain • Pain treatment • Acupuncture • Herbal therapy • Hypnosis • Tai chi • Massage therapy • Biofeedback • Evidence
The number of patients who utilize complementary and alternative medicine as a treatment of pain either in lieu of, or concurrent with, standard conventional treatments continues to grow. Over the last 20 years, Americans have sought a more "natural" or "holistic" approach to treatment of medical problems in general and pain in particular . According to a 2007 National Institute of Health (NIH) survey, acupuncture, one of the more popular forms of alternative medicine, was utilized by 3.1 million Americans, nearly 1% of the population, within the prior year . Among patients with unrelieved pain, there is an undertone of dissatisfaction with conventional treatment and a clear thirst for alternative strategies to combat their painful condition. While research into the mechanisms, side effect profiles, and efficacies of these alternative therapies has increased in recent years, much more remains unknown and untested. Herein, we review the literature on complementary and alternative medicine for pain, with particular emphasis on evidence-based assessments pertinent to the most common alternative therapies including acupuncture, herbal therapy, massage therapy, hypnosis, tai chi, and biofeedback.
Acupuncture is considered an ancient practice of traditional Chinese medicine (TCM) that began thousands of years ago. The basic principle of TCM relates to the concept of "qi" (or energy flow), whereby sickness results from the disruption of the flow of qi or imbalance between the yin and yang (opposing and inseparable life forces). Acupuncture describes a technique involving the stimulation of specific anatomical points on the human body. Furthermore, these acupuncture points, of which there are anywhere from 600 to 2000, are organized by specific energy pathways called meridians, which range in number from 14 to 20 . According to the theory behind acupuncture, an internal imbalance between yin and yang can block the flow of qi, whereby acupuncture can restore balance and harmony within the body.
While acupuncture has been practiced worldwide for centuries, its widespread use in the United States began in the 1970 s. In 1976, California became the first state to institute a formal license for the practice of acupuncture, and now over 40 other states have adopted similar regulatory practice. In 1997, the NIH Consensus Development Conference on Acupuncture reviewed available data on acupuncture and concluded, "There are reasonable studies (although sometimes only single studies) showing relief of pain with acupuncture..." . Subsequently, the NIH has developed an Office of Alternative Medicine, which is now known as the National Center for Complementary and Alternative Medicine (NCCAM). Today, NCCAM funds clinical trials to evaluate the efficacy of acupuncture.
As the number of practitioners providing acupuncture and the evidence base supporting the practice grow, so do the number of Americans who seek alternatives to conventional medicine. In a 2007 survey from the NIH, an estimated 3.1 million Americans had acupuncture treatment within the prior year; back pain ranked as the most common condition for which treatment was sought, followed by joint pain, neck pain, and headaches .
The validity of acupuncture for the treatment of pain is based on a body of evidence showcasing the neurophysiologic basis of its efficacy. In 1987, Pomeranz  theorized and then proved that acupuncture's effect begins with stimulation of Aδ and C-afferent fibers in muscle. Afferent signals then are transmitted to the spinal cord, midbrain, and hypothalamus. These signals also trigger the release of multiple mediators along its pathway, including endogenous opioids, such as dynorphin and enkephalins, and adrenocorticotropic hormone in the hypothalamus. Furthermore, the release of neurotransmitters such as serotonin, dopamine, and norepinephrine has been shown to cause both pre- and postsynaptic inhibition of central pain pathways [5••]. Another study by Han  demonstrated that the analgesic effects of acupuncture could be conferred from one animal to another via transfer of cerebrospinal fluid. Other studies have shown that acupuncture analgesia can be reversed by the opioid antagonist naloxone, demonstrating acupuncture's release of endogenous opioids . Studies on electroacupuncture (EA) have shown that low-frequency EA releases enkephalin and β-endorphin, while high-frequency EA releases dynorphin .
Several studies over the past few years have used the advanced technology of functional magnetic resonance imaging (fMRI) to visually identify the effects of acupuncture on the central nervous system. Wu et al.  used fMRI to demonstrate that acupuncture activates the hypothalamus and nucleus accumbens. Further, Zhang et al.  demonstrated that EA stimulated changes in the somatosensory and the medial prefrontal cortices, areas traditionally associated with both the sensory and emotional aspects of pain. Finally, Napadow et al.  compared traditional acupuncture with EA (tactile stimulation was used as a control), and discovered that low-frequency EA caused more fMRI changes compared to traditional acupuncture, and additionally demonstrated that both types of acupuncture produced greater fMRI changes when compared to tactile stimulation. Similar to previous studies indicating central nervous system activation from acupuncture, imaging revealed deactivation of the limbic and paralimbic areas of the brain, including the amygdala, hippocampus, and frontal and temporal lobes [5••], .
A Cochrane review in 2006 examined 10 randomized controlled trials that looked at acupuncture treatment of chronic neck pain (>90 days). A total of 661 patients were included in the meta-analysis. The authors concluded that there was moderate evidence that acupuncture was more effective than sham acupuncture, both immediately posttreatment and at 3-month follow-up . In another study, Vas et al.  compared acupuncture with transcutaneous nerve stimulation for the treatment of chronic neck pain. In total, 123 patients were randomly assigned to one of the two groups, with the primary end point being pain intensity of the neck with motion after five treatment sessions. The authors were able to demonstrate a significant reduction in pain intensity using the visual analogue scale in the acupuncture group.
A Cochrane review conducted in 2005 analyzed nine randomized controlled trials of patients with shoulder pain (>3 weeks duration). Based on the studies included in the meta-analysis, most of the patients had been diagnosed with either adhesive capsulitis or rotator cuff injury. However, when acupuncture was compared to placebo or other interventions (steroid injection or physiotherapy), the studies were neither statistically significant nor clinically significant . This led the authors to conclude that there was little evidence to support or refute the use of acupuncture for shoulder pain. However, a randomized controlled trial from 2009 looked at the efficacy of acupuncture as treatment of chronic shoulder pain in patients with a diagnosis of osteoarthritis or rotator cuff tendonitis (>8 weeks). When compared to sham nonpenetrating acupuncture, the mean total Shoulder Pain and Disability Index score improved in all three groups; however, the change was clinically significant only in the two acupuncture groups .
Trinh et al.  conducted a systematic review of six randomized controlled trials looking at the efficacy of acupuncture for lateral epicondyle pain (ie, tennis elbow). All six studies demonstrated positive results, leading the authors to conclude that there is evidence that acupuncture is effective in the short-term relief of lateral epicondyle pain. However, there were some significant limitations of the studies analyzed, including small sample sizes and variability in the definition of short-term pain relief
In a Cochrane review in 2009, Linde et al.  examined acupuncture for tension-type headaches. The authors analyzed 11 randomized controlled trials totaling 2,317 participants. Two of the large trials compared acupuncture and basic care to basic care alone (standard pain medications) and found that 47% of patients in the acupuncture group had at least a 50% decrease in the number of headache days versus 16% in the control groups. Acupuncture was compared with "sham" acupuncture (needles were inserted at incorrect points or did not penetrate the skin) in six trials, and 51% of patients in the acupuncture group were found to have at least a 50% decrease in the number of headache days compared to 41% in the sham group. Based on their meta-analysis, the authors concluded that the evidence suggests that acupuncture could be a valuable option for patients suffering from frequent tension-type headache.
Dr. Adam J Carinci, MD, is a nationally recognized and sought after clinician, expert witness, and speaker with over a decade of Pain Medicine experience. He is double-board certified in both Anesthesiology and in Pain Medicine and maintains an active, full time medical practice. Dr. Carinci is Chief of the Pain Management Division and Director of the Pain Treatment Center at the University of Rochester Medical Center and an Associate Professor at the University of Rochester School of Medicine.
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