Traditional Chinese Acupuncture and Placebo (Sham) Acupuncture Are Differentiated by Their Effects on μ-Opioid Receptors (MORs)
Harris et al. · NeuroImage · 2009
Evidence Level
MODERATEOBJECTIVE
To investigate the effects of traditional versus sham acupuncture on the brain's μ-opioid receptors (MOR)
WHO
20 women with fibromyalgia (mean age 44.3 years)
DURATION
4 weeks with 9 treatment sessions
POINTS
GV-20, auricular Shenmen, LI-4, LI-11, SP-6, LR-3, GB-34, ST-36 bilateral
🔬 Study Design
Traditional Acupuncture
n=10
9 needles with insertion and manipulation to obtain De Qi
Sham (Placebo)
n=10
Non-penetrating stimulation at non-acupuncture points
📊 Results in numbers
Brain regions with increased MOR after traditional acupuncture (short-term)
Brain regions with increased MOR after traditional acupuncture (long-term)
Pain reduction in the traditional acupuncture group
Pain reduction in the sham group
📊 Outcome Comparison
Opioid Receptor Changes (short-term)
Opioid Receptor Changes (long-term)
This study showed that traditional acupuncture affects the brain differently from placebo, increasing the availability of receptors that naturally control pain. This suggests that acupuncture has its own mechanisms of action and is not merely a placebo effect.
Article summary
Plain-language narrative summary
This pioneering study investigated how traditional Chinese acupuncture and placebo (sham) treatment differently affect μ-opioid receptors (MOR) in the brain of patients with chronic pain. The researchers used an advanced neuroimaging technology called PET (positron emission tomography) to observe in real time the changes in the brain receptors responsible for natural pain control. Twenty women diagnosed with fibromyalgia were randomly divided into two groups: one received traditional Chinese acupuncture with real insertion of needles at specific points, and the other received sham (placebo) treatment with non-penetrating stimulation at locations that are not acupuncture points. The protocol included 9 acupuncture points traditionally used for pain, including GV-20 (at the top of the head), auricular Shenmen (in the ear), and points on the arms and legs such as LI-4, ST-36, and SP-6.
Over four weeks, both groups received 9 treatment sessions. The results revealed marked differences in the brain mechanisms between the two treatments. Traditional acupuncture caused significant increases in the availability of μ-opioid receptors in 14 brain regions important for pain processing, including the cingulate cortex, insula, nucleus accumbens, thalamus, and amygdala. These increases were observed both immediately after treatment (short-term effects) and after the full 4 weeks of therapy (long-term effects).
In contrast, the group receiving sham treatment showed small reductions or no changes in the availability of these receptors, a pattern more consistent with previously documented placebo effects. Notably, the brain regions that showed the greatest increases in opioid receptors after traditional acupuncture were the same that correlated with greater clinical pain reduction. This suggests that increased availability of these receptors may be directly related to the therapeutic benefits of acupuncture. Both groups experienced pain reduction (4.0 points with traditional acupuncture vs 2.9 points with sham), but the underlying brain mechanisms were completely different.
This finding has important implications for understanding why many clinical studies of acupuncture fail to demonstrate superiority over placebo: both may be effective for pain, but operate through distinct neurobiologic pathways. The study suggests that acupuncture may work by 'normalizing' opioid receptor availability in patients with fibromyalgia, who have previously been shown to have deficiencies in these receptors. Limitations include the small sample size and the specific population (only women with fibromyalgia), which may limit the generalizability of the results. In addition, the study cannot determine whether the observed effects are due to the specific location of the acupuncture points or to skin penetration.
Strengths
- 1First direct evidence of acupuncture effects on human μ-opioid receptors
- 2Use of advanced PET neuroimaging for objective analysis
- 3Randomized controlled design with appropriate sham group
- 4Analysis of short- and long-term effects
Limitations
- 1Small sample (only 20 participants)
- 2Specific population (only women with fibromyalgia)
- 3Does not distinguish between effects of point location vs skin penetration
- 4Need for replication in larger and more diverse populations
Expert Commentary
Prof. Dr. Hong Jin Pai
PhD in Sciences, University of São Paulo
▸ Clinical Relevance
This work by Harris et al. represents a watershed in the neurobiology of acupuncture by providing the first direct evidence, in human beings, that traditional acupuncture modulates the availability of μ-opioid receptors in brain regions central to pain processing. For the clinician treating fibromyalgia — a notoriously refractory condition, with a limited and often poorly tolerated pharmacologic arsenal — understanding that acupuncture acts on neurobiologic pathways objectively distinct from those of placebo fundamentally changes the conversation with the patient and with the multidisciplinary team. The activation pattern in structures such as the cingulate cortex, insula, nucleus accumbens, thalamus, and amygdala is exactly the deficient circuit in fibromyalgia, reinforcing the rationale for indicating acupuncture as an intervention directed at an identifiable pathophysiologic mechanism, and not as an empirical last-line resource.
▸ Notable Findings
The most robust and clinically thought-provoking finding is the dissociation between apparent analgesic efficacy and underlying mechanism: both groups reduced pain — 4.0 points in traditional acupuncture versus 2.9 in sham — but through radically different neurobiologic pathways. While the sham group showed modest reductions or no change in MOR availability, traditional acupuncture produced significant increases in 14 regions in the short term and 10 regions after four weeks, suggesting sustained receptor neuroplasticity. This long-term phenomenon is particularly relevant: it is not an acute endorphin effect, but receptor remodeling. The correlation between regions with greater MOR upregulation and the magnitude of clinical pain improvement provides a mechanistic substrate that connects the bench finding directly to the benefit observed in the office.
▸ From My Experience
In my practice at the HC-FMUSP Pain Center, fibromyalgia has always been one of the diagnoses that most tests our ability to compose rational therapeutic strategies. I usually observe the first analgesic responses between the third and fifth sessions, with more consistent functional improvement emerging around the eighth session — which aligns well with the four-week, nine-session window used in this protocol. For maintenance, I usually work with cycles of 10 to 12 sessions followed by progressive spacing, because patients with fibromyalgia tend to relapse if acupuncture is abruptly discontinued. I routinely combine it with a supervised gradual aerobic exercise program and, when indicated, with duloxetine or pregabalin at doses lower than would be needed in monotherapy. The patient profile that responds best, in my observation, is one with a predominant central sensitization component and without severely decompensated psychiatric comorbidity. This article confirms to me why I insist on acupuncture with De Qi in this population: needle manipulation is not a technical detail, it is probably the trigger of the receptor mechanism documented here.
Full original article
Read the full scientific study
NeuroImage · 2009
DOI: 10.1016/j.neuroimage.2009.05.083
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.
Related articles
Based on this article’s categories