How might acupuncture work? A systematic review of physiologic rationales from clinical trials
Moffet · BMC Complementary and Alternative Medicine · 2006
Evidence Level
STRONGOBJECTIVE
To analyze how many acupuncture clinical trials propose physiologic explanations for how acupuncture works
WHO
Review of 79 acupuncture clinical trials published in English in 2005
DURATION
Analysis of studies published in a single specific year (2005)
POINTS
Varied — studies used point selection based on traditional indications
🔬 Study Design
Trials with physiologic explanation
n=53
Proposed neurologic or physiologic mechanisms
Trials without explanation
n=26
No physiologic explanation offered
📊 Results in numbers
Trials offering a physiologic explanation
Proposed neurochemical mechanisms
Trials with positive results
Total trials analyzed
Percentage highlights
📊 Outcome Comparison
Types of physiologic explanations proposed
This study analyzed how researchers explain the way acupuncture works in clinical trials. It found that two thirds of studies propose that acupuncture works primarily through the release of the body's natural chemical substances, such as endorphins, regardless of the specific points used.
Article summary
Plain-language narrative summary
This study represents an important methodologic analysis of how the scientific community approaches the mechanisms of action of acupuncture. The author conducted a systematic review of 79 acupuncture clinical trials published in English during 2005, with the aim of determining how many studies offered physiologic explanations for how acupuncture might work. The results revealed that 67% of the studies (53 of 79) proposed some type of physiologic explanation, while 33% offered no explanation of mechanisms of action. Among the studies that offered explanations, the dominant theory involved neurochemical mechanisms, particularly the release of endogenous opioids such as beta-endorphins, enkephalins, and dynorphins, or neurotransmitters such as serotonin.
This neurochemical explanation was used not only for analgesia but also for diverse conditions such as nausea, insomnia, obesity, Parkinson disease, and hypertension. Other proposed mechanisms included segmental effects of the nervous system (gate control theory), autonomic nervous system regulation, local effects on tissues, and changes in brain function detected by functional magnetic resonance imaging. The study found that having a physiologic explanation was not associated with the type of condition treated (except stroke, in which no study offered an explanation), positive or negative results, country of origin, source of funding, or type of journal. Interestingly, no study proposed that the neurochemical effects of acupuncture depended on the specific selection of points, nor did the studies make important distinctions among different stimulation methods (needles, pressure, electricity, laser).
This observation suggests that acupuncture may work by stimulating general self-regulatory processes, regardless of the specific technique used. The author argues that this hypothesis would explain the reported benefits of acupuncture in such diverse pathologic conditions. The study highlights the importance of proposing physiologic explanations in clinical trials, not only for scientific purposes but also to help in the selection of appropriate controls and the exclusion of placebo effects. The lack of mechanistic hypotheses can hinder appropriate study design, especially in the choice of control interventions.
Limitations include the analysis of only English-language articles and the simple binary classification (having or not having an explanation), without assessing the quality or validity of the proposed explanations. The study represents a valuable contribution to understanding how acupuncture research addresses fundamental mechanistic questions.
Strengths
- 1Comprehensive analysis of all acupuncture clinical trials from a specific year
- 2Clear and reproducible methodology
- 3Identification of important patterns in physiologic explanations
- 4Analysis of multiple contextual variables
Limitations
- 1Inclusion of only English-language articles
- 2Limited analysis of the quality of proposed explanations
- 3Sample limited to a single year of publications
- 4Simple binary classification of explanations
Expert Commentary
Prof. Dr. Hong Jin Pai
PhD in Sciences, University of São Paulo
▸ Clinical Relevance
The question of how acupuncture works is not merely academic — it directly informs how we design protocols, select points, and justify the intervention before ethics committees and payers. Moffet demonstrated that, in 2005, two thirds of acupuncture clinical trials already proposed some physiologic mechanism, with neurochemical pathways — release of endogenous opioids such as beta-endorphins, enkephalins, and dynorphins, plus serotonin — accounting for 62% of those explanations. For the clinician who deals daily with chronic pain, oncologic nausea, insomnia, and hypertension, this mechanistic convergence is relevant: it suggests that acupuncture mobilizes self-regulatory pathways shared across apparently distinct conditions. The finding that physiologic explanations did not vary by country of origin, funding source, or positive or negative outcome reinforces that this is a field mature enough to support replicable hypotheses, and not merely findings dependent on publication bias.
▸ Notable Findings
The most provocative point of this review is precisely what the investigators did not do: none of the 53 studies that proposed neurochemical mechanisms postulated that these effects depended on specific point selection. Nor were systematic distinctions made among needles, pressure, electrostimulation, or laser. This calls into question the point-specific narrative that dominates much of classical teaching and opens space for a more integrative understanding — acupuncture as a nonspecific yet reproducible stimulus of self-regulatory circuits. Complementarily, the detection of functional brain changes by functional magnetic resonance imaging already appeared as an explanatory category in 2005, anticipating a line of research that would become central in the following decade. The fact that 77% of the trials reported positive results, distributed independently of the presence or absence of a mechanistic explanation, also deserves attention: it suggests that the clinical effect precedes and transcends our current ability to explain it.
▸ From My Experience
At the Pain Center of HC-FMUSP, we deal daily with the tension between the classical model of point selection and the growing evidence that systemic neuromodulation may be the main therapeutic vector. Reading Moffet's work resonates with what I have observed over decades: patients with multifocal chronic pain, fibromyalgia, and even comorbid insomnia frequently respond to relatively simple protocols using distal points of long tradition, in a way that is difficult to explain by anatomic specificity alone. I usually see the first signs of response between the third and fifth session, and in established chronic pain cases I advise patients to undergo cycles of eight to twelve sessions before reassessing the plan. Combination with supervised aerobic exercise and, when necessary, adjuvant analgesics consistently enhances results. The profile that responds best, in my experience, is the patient with nociplastic pain, anxious, with an evident autonomic component — exactly the patient in whom the neurochemical pathway described in this review makes the most pathophysiologic sense.
Full original article
Read the full scientific study
BMC Complementary and Alternative Medicine · 2006
DOI: 10.1186/1472-6882-6-25
Access original articleScientific Review
Marcus Yu Bin Pai, MD, PhD
CRM-SP: 158074 | RQE: 65523 · 65524 · 655241
PhD in Health Sciences, University of São Paulo. Board-certified in Pain Medicine, Physical Medicine and Rehabilitation, and Medical Acupuncture. Scientific review and curation of every entry in this library.
Learn more about the author →Medical disclaimer: This content is for educational purposes only and does not replace consultation, diagnosis, or treatment by a qualified professional. Some information may be assisted by artificial intelligence and is subject to inaccuracies. Always consult a physician.
Content reviewed by the medical team at CEIMEC — Integrated Centre for Chinese Medicine Studies, a reference in Medical Acupuncture for over 30 years.
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