The system of acupuncture can be traced back to China and has probably been practiced for thousands of years. The therapy became an international crossover hit much more recently. In 1972 President Richard M. Nixon visited the People’s Republic, and the Western journalists accompanying him described spectacular successes of acupuncture in anesthesia and pain control–including cesarean sections in which the women got only needles and no anesthetics. Even as acupuncture has grown in popularity, though, it has never been able to shake suspicions that it is merely an esoteric sham treatment. Over the years, researchers have discovered that the simple act of placing a needle through the skin does seem to benefit some patients and trigger a surprising array of physiological activity. But it is also clear that the technique may have powerful placebo effects that could explain its success. Sorting out the relative contributions of neurobiology and psychology to acupuncture’s power has become the yin and yang for researchers in this field. The traditional explanation for how acupuncture heals is based on the idea that a person’s life energy–Qi–runs along certain lines, or meridians, through the body. Disease is believed to result from disruption in this flow. Qi is said to reach the upper level of the skin at more than 350 specific points, and these points are where a therapist can influence the streams of energy, restore balance and heal. One of the problems of trying to pin down the science of acupuncture is that the term can describe a wide variety of therapeutic approaches that diverged in each country that adopted the Chinese healing art. French, Japanese and Korean acupuncture versions exist, for example, and these variations do not completely agree on which Qi points to use for each illness. Many techniques are also used to stimulate these points: heat, pressure–even lasers. But the most famous, and for that reason the best studied, is the use of metal needles to penetrate the skin, followed by electrical or manual stimulation. Another issue is that no one has been able to discover anatomical or physical structures that correspond to Qi or to the meridians along which the energy runs. Although the existence of Qi remains unproved, plenty of evidence confirms that needles can affect biology. The best studied of these effects are those that influence pain, starting with groundbreaking studies on pain relief by Ji-Sheng Han of Peking University’s Neuroscience Research Center. In the 1970s and 1980s his group demonstrated that the body can release natural, or endogenous, painkillers called endorphins in response to the needles. Han performed electronic acupuncture on rats and then infused their blood into a control group that had never been treated. After treatment, the animals in both groups were less sensitive to pain, apparently because the endogenous painkillers were transferred along with the blood. Pricks vs. Pain Many years and experiments later, acupuncture is known to operate on many levels that control pain. The stimulation of nerve fibers at the point of insertion causes the secretion of many factors known to influence pain processing. Enkephalin and dynorphin, natural opiates produced by the body, are released and inhibit the electrical arousability of the nerve cells in the spinal cord. This mechanism is how practitioners explain the direct painkilling effect of acupuncture, the so-called immediate analgesic effect. As long as the needle is in the skin, the stimulus from the needle diverts the stimulus from the pain being fought. Experts such as physician Marcus Baecker of the department of internal and integrative medicine at the University of Duisburg-Essen in Germany believe a second mechanism accounts for longer-lasting relief. Inhibitory synapses in an area of the spinal cord called the posterior horn can cause an enduring reduction in the conductivity of nerve fibers passing the signals upward toward the brain, so that the real pain no longer reaches the cerebrum–and, as a result, is not consciously perceived. But acupuncture’s influence also runs deep into the brain. Scientists at the China Academy for Traditional Chinese Medicine in Beijing and at Harvard Medical School published studies in 2000 and 2002 that used functional magnetic resonance imaging (fMRI), a technique that monitors neuronal activity, to see whether needles inserted in the hand changed brain function. They found decreased activity in the hippocampus, hypothalamus and other components of the limbic system, which is known to be involved in pain sensation. Changes were also recorded in the activity of the somatosensory cortex, a brain region involved in processing pain, when the researchers probed certain acupuncture points. Acupuncture-stimulated release of hormones, neurotransmitters such as serotonin, and endorphins may explain some of the other physical effects of this therapy, including changes in blood flow and immune cell function. That acupuncture can trigger the release of multiple factors and cause shifts in brain function lends credence to the idea that it can influence many different systems of the body. And some clinical evidence supports this idea as well. A 1997 report sponsored by the National Institutes of Health, for example, concluded that “clear evidence” indicates that needle acupuncture is an effective treatment for a variety of conditions, including nausea after surgery and chemotherapy and vomiting caused by morning sickness during pregnancy. The report noted “reasonable evidence” for the ability of acupuncture to lessen pain from surgery and menstrual cramps. In addition, unpleasant side effects from the needles were found to be less frequent than those associated with many conventional treatments. With all this biological evidence, it might seem that the case for acupuncture’s effectiveness is all sewn up. But whereas some patients do seem to fare better after acupuncture treatment, it is not clear that the healing is caused by the needles themselves. For Dominik Irnich of the department of anesthesiology at the University of Munich, some of the secret of this Chinese export lies in its psychological effects: “The patients simply get a lot more attention here. The patient and doctor are not separated by a desk–instead he both touches her with his hands and observes her carefully. In addition, there are continual conversations about problems and symptoms–that alone, as a rule, has a positive impact on the course of disease.” Placebo or Not Placebo Determining how much of the effect of acupuncture is placebo has been difficult. It is clear, though, that some of the biological effects do not rely on the patient even being aware of the treatment, as demonstrated in a 2004 study by Winfried Meissner’s research team at the Friedrich-Schiller University of Jena in Germany. The researchers anesthetized 16 subjects and exposed them to what, in a conscious person, would have been painful electric shocks to the right forefinger, while treating them at acupuncture points in the leg. During the procedure, they documented subjects’ reactions using a method that measures evoked potential in their brain waves. These are characteristic lines in the electroencephalogram (EEG), which are produced in response to the stimuli–and correlate with pain. Although the subjects were not conscious of the needles, their arousal potentials were reduced by the acupuncture. Yet the real test of whether a treatment is better than a placebo is to compare it with one in a placebo-controlled trial. For pharmaceuticals, that only requires making a sugar pill convincing enough to impersonate the drug under evaluation. Convincing someone that a needle has gone through his or her skin–when it has not–is not an easy trick, however. A Deceptive Needle That challenge has not stopped researchers from trying. In 1998 Konrad Streitberger and his colleagues at the Clinic for Anesthesiology of the University of Heidelberg in Germany reported their development of a needle that barely pricked the surface but was designed to look as if it had penetrated. As a result, the subjects–although they felt the needles–did not know that the needle was inserted into only the top layer of skin. The Heidelberg group found that the subjects who received a real acupuncture treatment evaluated the procedure as considerably more successful than did the patients who received placebo acupuncture. Other trials, however, have come to different conclusions. In 2005 Irnich and his colleagues studied 270 people with tension-type headaches who were treated with authentic acupuncture, superficial needles at nonacupuncture points or no treatment at all. They found that patients who received acupuncture recorded significantly fewer headaches than patients who received no treatment. But no difference in headache relief occurred between the placebo and real acupuncture. Other trials have found that sham acupuncture’s effects lie between those of traditional acupuncture and no treatment. Exactly how this mixed bag of results from placebo-controlled trials should be interpreted is a controversial topic. One possible explanation is that for some conditions acupuncture may work through precise biological mechanisms triggered by the needles, whereas for others its effect may be nonspecific and driven by psychological placebo effects. It is also possible that the needles may have effects at many depths: pressure at the surface, a minimal penetration of the skin, and at full insertion. Some effects might rely on the exact placement of the needle, and some may not. If this is true, then creating a placebo control for acupuncture may be impossible. The fact that acupuncture shows promise as a primary treatment for some conditions and as an addition to conventional therapy for others has convinced many experts that it is worth conducting larger trials to sort out some of these issues. Such research also offers scientists a rare opportunity: the chance to improve on a therapy that is already millennia old.
Even as acupuncture has grown in popularity, though, it has never been able to shake suspicions that it is merely an esoteric sham treatment. Over the years, researchers have discovered that the simple act of placing a needle through the skin does seem to benefit some patients and trigger a surprising array of physiological activity. But it is also clear that the technique may have powerful placebo effects that could explain its success. Sorting out the relative contributions of neurobiology and psychology to acupuncture’s power has become the yin and yang for researchers in this field.
The traditional explanation for how acupuncture heals is based on the idea that a person’s life energy–Qi–runs along certain lines, or meridians, through the body. Disease is believed to result from disruption in this flow. Qi is said to reach the upper level of the skin at more than 350 specific points, and these points are where a therapist can influence the streams of energy, restore balance and heal.
One of the problems of trying to pin down the science of acupuncture is that the term can describe a wide variety of therapeutic approaches that diverged in each country that adopted the Chinese healing art. French, Japanese and Korean acupuncture versions exist, for example, and these variations do not completely agree on which Qi points to use for each illness. Many techniques are also used to stimulate these points: heat, pressure–even lasers. But the most famous, and for that reason the best studied, is the use of metal needles to penetrate the skin, followed by electrical or manual stimulation. Another issue is that no one has been able to discover anatomical or physical structures that correspond to Qi or to the meridians along which the energy runs.
Although the existence of Qi remains unproved, plenty of evidence confirms that needles can affect biology. The best studied of these effects are those that influence pain, starting with groundbreaking studies on pain relief by Ji-Sheng Han of Peking University’s Neuroscience Research Center. In the 1970s and 1980s his group demonstrated that the body can release natural, or endogenous, painkillers called endorphins in response to the needles. Han performed electronic acupuncture on rats and then infused their blood into a control group that had never been treated. After treatment, the animals in both groups were less sensitive to pain, apparently because the endogenous painkillers were transferred along with the blood.
Pricks vs. Pain Many years and experiments later, acupuncture is known to operate on many levels that control pain. The stimulation of nerve fibers at the point of insertion causes the secretion of many factors known to influence pain processing. Enkephalin and dynorphin, natural opiates produced by the body, are released and inhibit the electrical arousability of the nerve cells in the spinal cord. This mechanism is how practitioners explain the direct painkilling effect of acupuncture, the so-called immediate analgesic effect. As long as the needle is in the skin, the stimulus from the needle diverts the stimulus from the pain being fought.
Experts such as physician Marcus Baecker of the department of internal and integrative medicine at the University of Duisburg-Essen in Germany believe a second mechanism accounts for longer-lasting relief. Inhibitory synapses in an area of the spinal cord called the posterior horn can cause an enduring reduction in the conductivity of nerve fibers passing the signals upward toward the brain, so that the real pain no longer reaches the cerebrum–and, as a result, is not consciously perceived.
But acupuncture’s influence also runs deep into the brain. Scientists at the China Academy for Traditional Chinese Medicine in Beijing and at Harvard Medical School published studies in 2000 and 2002 that used functional magnetic resonance imaging (fMRI), a technique that monitors neuronal activity, to see whether needles inserted in the hand changed brain function. They found decreased activity in the hippocampus, hypothalamus and other components of the limbic system, which is known to be involved in pain sensation. Changes were also recorded in the activity of the somatosensory cortex, a brain region involved in processing pain, when the researchers probed certain acupuncture points.
Acupuncture-stimulated release of hormones, neurotransmitters such as serotonin, and endorphins may explain some of the other physical effects of this therapy, including changes in blood flow and immune cell function. That acupuncture can trigger the release of multiple factors and cause shifts in brain function lends credence to the idea that it can influence many different systems of the body. And some clinical evidence supports this idea as well.
A 1997 report sponsored by the National Institutes of Health, for example, concluded that “clear evidence” indicates that needle acupuncture is an effective treatment for a variety of conditions, including nausea after surgery and chemotherapy and vomiting caused by morning sickness during pregnancy. The report noted “reasonable evidence” for the ability of acupuncture to lessen pain from surgery and menstrual cramps. In addition, unpleasant side effects from the needles were found to be less frequent than those associated with many conventional treatments.
With all this biological evidence, it might seem that the case for acupuncture’s effectiveness is all sewn up. But whereas some patients do seem to fare better after acupuncture treatment, it is not clear that the healing is caused by the needles themselves.
For Dominik Irnich of the department of anesthesiology at the University of Munich, some of the secret of this Chinese export lies in its psychological effects: “The patients simply get a lot more attention here. The patient and doctor are not separated by a desk–instead he both touches her with his hands and observes her carefully. In addition, there are continual conversations about problems and symptoms–that alone, as a rule, has a positive impact on the course of disease.”
Placebo or Not Placebo Determining how much of the effect of acupuncture is placebo has been difficult. It is clear, though, that some of the biological effects do not rely on the patient even being aware of the treatment, as demonstrated in a 2004 study by Winfried Meissner’s research team at the Friedrich-Schiller University of Jena in Germany. The researchers anesthetized 16 subjects and exposed them to what, in a conscious person, would have been painful electric shocks to the right forefinger, while treating them at acupuncture points in the leg. During the procedure, they documented subjects’ reactions using a method that measures evoked potential in their brain waves. These are characteristic lines in the electroencephalogram (EEG), which are produced in response to the stimuli–and correlate with pain. Although the subjects were not conscious of the needles, their arousal potentials were reduced by the acupuncture.
Yet the real test of whether a treatment is better than a placebo is to compare it with one in a placebo-controlled trial. For pharmaceuticals, that only requires making a sugar pill convincing enough to impersonate the drug under evaluation. Convincing someone that a needle has gone through his or her skin–when it has not–is not an easy trick, however.
A Deceptive Needle That challenge has not stopped researchers from trying. In 1998 Konrad Streitberger and his colleagues at the Clinic for Anesthesiology of the University of Heidelberg in Germany reported their development of a needle that barely pricked the surface but was designed to look as if it had penetrated. As a result, the subjects–although they felt the needles–did not know that the needle was inserted into only the top layer of skin. The Heidelberg group found that the subjects who received a real acupuncture treatment evaluated the procedure as considerably more successful than did the patients who received placebo acupuncture.
Other trials, however, have come to different conclusions. In 2005 Irnich and his colleagues studied 270 people with tension-type headaches who were treated with authentic acupuncture, superficial needles at nonacupuncture points or no treatment at all. They found that patients who received acupuncture recorded significantly fewer headaches than patients who received no treatment. But no difference in headache relief occurred between the placebo and real acupuncture. Other trials have found that sham acupuncture’s effects lie between those of traditional acupuncture and no treatment.
Exactly how this mixed bag of results from placebo-controlled trials should be interpreted is a controversial topic. One possible explanation is that for some conditions acupuncture may work through precise biological mechanisms triggered by the needles, whereas for others its effect may be nonspecific and driven by psychological placebo effects. It is also possible that the needles may have effects at many depths: pressure at the surface, a minimal penetration of the skin, and at full insertion. Some effects might rely on the exact placement of the needle, and some may not. If this is true, then creating a placebo control for acupuncture may be impossible.
The fact that acupuncture shows promise as a primary treatment for some conditions and as an addition to conventional therapy for others has convinced many experts that it is worth conducting larger trials to sort out some of these issues. Such research also offers scientists a rare opportunity: the chance to improve on a therapy that is already millennia old.
