Acupuncture is one of the oldest systems of traditional medicine. With roots in China, this medical system is more than 2000 years old. It differs from various other medical systems as it does not involve taking any herbs or substances. Instead, it involves inserting small needles at specific predefined points. From the 20^th century onwards, it has continued to gain prominence in the Western world, although many remain skeptical about efficacy.

These days, researchers want to know the exact mechanism of action of any medical system. They only trust the therapy if it has been proven as effective in randomized placebo-controlled clinical trials. Acupuncture has been the subject of many such trials, and its usefulness has been established in certain pain-associated conditions, mood disorders, and even in some diseases of internal organs. This led to the recognition of this medical system by many healthcare providers and medical organizations. In the US, acupuncture is recognized as complementary medicine. The WHO also recommends it for a number of specific medical conditions.

Clinical evidence of efficiency

Hundreds of clinical trials provide evidence of the effectiveness of acupuncture in various medical conditions. Among the most relevant trials are the so-called German mega-trials named ARC, ART, COMP, and GERAC. The primary focus of these trials has been pain relief in various musculoskeletal conditions. GERAC and ART were high quality random clinical trials investigating low back pain. These trials compared real acupuncture with sham acupuncture and standard care. Sham acupuncture involved needling without the use of conventional acupuncture points. Whereas standard care included the use of physiotherapy, exercise therapy, and NSAIDs (non-steroidal anti-inflammatory drugs). Results were measured after three months, and the response was defined as adequate if there was an improvement of more than 33% on the pain scale (the Von Korff Chronic Pain Grade Scale). After 6-months, the response rate with real acupuncture was 47.6%, while it was 44.2% with sham acupuncture, and 27.4% with standard care. Though these trials clearly demonstrated the efficacy of acupuncture, they also showed the effectiveness of sham acupuncture. Researchers think that this phenomenon is linked to psychogenic factors involved with back pain.

Interestingly, similar results were also demonstrated in various trials in the US. Though these trials show the usefulness of acupuncture in painful conditions, they also illustrate the value of psychogenic factors. Therefore, it is not surprising that acupuncture had also proven its utility in treating mood disorders and sleep disorders.

In Chinese medicine, the use of acupuncture is not limited to pain-related conditions. Thus, there is need for more extensive trials across a diverse range of diseases. The existing data do indicate that acupuncture may be an alternative approach for many difficult to treat chronic ailments.

Possible mechanisms

One of the areas of debate regarding acupuncture has been the difficulty in explaining its mechanism of action. As per traditional explanation, acupuncture is used to correct the flow of energy (Qi) in the body. This life energy flows through the fixed paths or highways in our body called meridians. Practitioners of acupuncture believe that in disease conditions there is a blockade of energy highways or meridians. Acupuncture is about creating the balance between the internal forces called Yin and Yang. However, the trouble is that modern science is not able to demonstrate or even understand the concepts of Qi, Yin, Yang, and Meridians.

In the last few decades, practitioners of modern science have made various attempts to explain the mechanism of action of acupuncture, and they came up with multiple theories.

• Measurable effects of acupuncture: One of the explanations is that needling does cause local changes and alterations in reflexes. It also has systemic effects, as it changes the working of the autonomous nervous system. Thus, acupuncture affects blood pressure, heart rate, levels of various hormones, and changes the levels of neurotransmitters. All of this results in pain relief and other beneficial effects.
• Local mechanotransduction: This is a theory promoted by a French physician in 1961, who wrote that acupuncture points have lower local resistance when compared to surrounding skin. He wrote that while normal dry skin has a resistance of 200,000 to 2 million Ohms, acupuncture points have a resistance of just 50,000 Ohms. The believers in this theory say that acupuncture causes minute traumas at the points of needle insertion and thus stimulates survival mechanisms of the body. Needling stimulates homeostasis, anti-inflammatory responses, tissue regeneration, and much more.
• Neurohumoral theory: it has been demonstrated that acupuncture is useful in pain relief, and naloxone blocks its analgesic effect. Thus, researchers propose that needling at specific points leads to the release of endogenous painkilling opiate-like substances such as enkephalins, endorphins, dynorphins and some other neurotransmitters like serotonin and noradrenaline.
• Gate-control theory: This theory states that needling stimulates large myelinated nerve fibers. These fibers carry tingling sensations and feelings of warmth, and can inhibit the painful sensation that is transmitted to the brain by much smaller C-fibers via spinal tracts.
• Postsynaptic inhibition: This is another explanation, which states that acupuncture results in the inhibition of pain through a central mechanism via disinhibition of RAF. This phenomenon typically works in cases of extreme trauma like loss of limb. This central mechanism has a role in protecting the body from extreme stress and pain.
• Autonomous nervous system: Proponents of this theory suggest that acupuncture works by changing the balance of sympathetic and parasympathetic nervous system.
• Morphogenetic singularity theory: This is one of the more complicated hypotheses that tries to explain the existence of meridians. Advocates of this theory explain the presence of non-neural communication pathways in the body. During embryonic development, when neurons are not yet formed, cells must communicate among themselves to direct development. Meridians are just the remains of these early communication paths, which are still present in the adult body.
• Visualization: In recent years, fMRI methods have advanced a lot, and in many clinical studies it has been demonstrated that stimulation of various acupuncture points by needling results in activation of different brain centers, thus explaining the mechanism of action of acupuncture. It is believed that both the elements of morphogenetic singularity theory (meridians) and components of the neurohumoral response are involved in the stimulation of the brain.

It is obvious that various theories have been used to describe the mechanism of action of acupuncture, and most probably there is more than one mechanism is involved. Clinical trials do seem to indicate that acupuncture is beneficial in specific health conditions. But the way it works still remains a mystery.

References

Dong, B., Chen, Z., Yin, X., Li, D., Ma, J., Yin, P., … Xu, S. (2017. The Efficacy of Acupuncture for Treating Depression-Related Insomnia Compared with a Control Group: A Systematic Review and Meta-Analysis. BioMed Research International, 2017, 9614810. doi: 10.1155/2017/9614810

Kawakita, K., & Okada, K. (2014) Acupuncture therapy: mechanism of action, efficacy, and safety: a potential intervention for psychogenic disorders? Biopsychosocial Medicine, 8, 4. doi: 10.1186/1751-0759-8-4

White, A., & Ernst, E. (2004) A brief history of acupuncture. Rheumatology, 43(5), 662–663. doi: 10.1093/rheumatology/keg005

Wong MC, Shen HJ (2010) Science-based Mechanisms to Explain the Action of Acupuncture. Journal of the Association of Traditional Chinese Medicine (UK), 17(2), 5-10.

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