A HAIR-THIN needle pricks the skin. What happens next depends on who you ask. A traditional Chinese practitioner will tell you that acupuncture manipulates the body’s vital energy, Qi (pronounced chee), balancing the opposing forces of Yin and Yang. When Yin and Yang are in harmony, Qi flows freely along pathways called meridians and you stay healthy, but when the Qi gets blocked you become ill. Inserting needles into points along a meridian unblocks Qi and restores the body’s healthy balance.
Western scientists explain it differently. They say inserting needles at acupuncture points stimulates the nervous system to release morphine-like substances that block pain signals. It may also trigger neurotransmitters and neurohormones, which influence such dynamic systems as circulation and the immune response.
Ever since acupuncture caught on in the West, we’ve been seeking to replace the Eastern mysticism with hard facts. But clinical trials so far have produced a disappointingly mixed bag of results that don’t seem to back up the anecdotal claims for the wonders of acupuncture. There might be a steadily building case for clinical relief of some types of pain and nausea. But the inconclusive studies still outweigh the positive ones.
Even though acupuncture has not measured up in trials, it has a long history, and plenty of researchers have instead turned their attention to how it might work. They believe that trials are not producing great results because we don’t know the best ways to test acupuncture. There’s enough evidence that it can work, they argue, and what we need to know is how to tap into its effectiveness. Maybe with a clear idea of a mechanism, we’d be in a much better position to test and use it.
At first, doctors thought the treatment made sense because of a theory about pain called “gate control”. They believed that the needles stimulated nerve fibres that transmit mild pain impulses, and that this somehow interrupted or blocked the more severe pain signals coming from the site of injury. But this didn’t really explain how the effects of acupuncture could persist after the needle was removed.
The first real success at putting acupuncture on a scientific footing came in 1976, when Bruce Pomeranz, a neuroscientist from the University of Toronto in Ontario, discovered that acupuncture works as an analgesic, triggering the release of endorphins – the body’s natural painkillers.
He found that mice could tolerate pain more easily after acupuncture, and that he could block the analgesic effect by injecting the mice with naloxone before applying the needles – the substance prevents endorphins binding to nerve cells. He believes that when the needle is inserted into the muscle, it stimulates small nerve fibres which in turn send impulses to the mid-brain and hypothalamus. Endorphins in these brain regions, along with other morphine-like substances, are released to block pain. Twenty-five years later, more than 2000 experiments worldwide support the endorphin theory.
More recent work suggests that how you apply the needles might affect which of these morphine-like chemicals are released – and hence what effect the acupuncture has on the patient. In traditional Chinese acupuncture, twisting or flicking the needles once they are in place can alter the effect. It seems that sending an alternating current through them – a technique known as electroacupuncture – might do the same.
You change which opioid substances are released during electroacupuncture by altering the frequency of the alternating current. Low-frequency (2 hertz) current, for example, triggers the release of enkephalins in the spinal cord and b-endorphins in the midbrain. High-frequency (100 Hz) stimulation, on the other hand, leads to dynorphin release in the spinal cord.
Of the millions of people in the West who have tried acupuncture, most are seeking relief from pain in hard-to-treat conditions such as lower back problems, headaches and osteoarthritis. But in the East, acupuncture is much more widely used. Ji-Sheng Han, Director of Neuroscience Research at Peking University in Beijing, thinks that endorphin signalling could make acupuncture useful for treating addiction as well as pain.
In a recent study of its use to help heroin addicts kick the habit, Han needled the Hoku point – the fleshy bit of skin between the thumb and forefinger – with 100 Hz for 30 minutes per day for two weeks. Withdrawal symptoms such as nausea and increased heart rate kick in just after addicts go “cold turkey”, he says, and dynorphins can help alleviate these symptoms.
A couple of weeks later comes the craving stage or chronic phase, which can last a lifetime. Han found cravings diminished in people treated with 2 Hz. This stimulates the release of endorphins, which act in a similar way to morphine and heroin, says Han. “It’s not enough to get you high, but it will make you feel much better.” So far, clinical trials done elsewhere have failed to confirm Han’s findings. And the technique has not proved effective for people trying to quit smoking. But Han thinks that the positive results from his study should encourage more trials. Used in the right way, acupuncture might have positive effects way beyond pain control.
Indeed, acupuncture may even influence how genes are expressed. In his latest experiments, Han used acupuncture to treat mice which had had many of their dopamine neurons severed to simulate Parkinson’s disease. After needling several times, he found an increase in a specific messenger RNA, one that codes for a nerve growth factor that helps to regenerate dopamine neurons.
Genes are also being used to explain why acupuncture simply doesn’t work for some patients, even if they strongly believe in it. According to Han and others, just as with conventional drugs, some people will naturally respond while others won’t because of their genetic make-up.
Han measured opioid release in 10 patients after they received low and high-frequency electroacupuncture. Half responded to the 2 Hz frequency, while nine responded to 100 Hz. In other words, the same person might produce dynorphins but not enkephalins. Han also suspects that the people who don’t respond at all might have a deficiency in one of the three types of opioid receptors, so they may produce the chemical but can’t react to it.
Another possibility is that because of their genes, some people may make too much of a substance that blocks opioids, known as cholecystokinin 8 (CCK8). If opioids are the Yin of acupuncture, this is the Yang. CCK8 builds up with each acupuncture treatment until it cancels out the painkilling effects altogether, leading to acupuncture tolerance.
Another thing that can vary the effect of acupuncture is where the needles are inserted. The Chinese tradition uses very detailed maps of different acupoints along the meridians to target the region to be treated. Recent brain scanning work seems to back the idea that different acupoints do have specific targets. Zang-Hee Cho, a radiologist at the University of California at Irvine, found that stimulating an acupuncture point on the little toe that is traditionally used to treat eye disorders triggers activity in the brain’s visual cortex (Proceedings of the National Academy of Sciences, vol 95, p 2670). In another study, he found a link between points on the ear and the auditory cortex.
Cho reckons that he is discovering new neural pathways that we simply weren’t able to visualise before. “Meridians were just a tool to explain acupuncture before we understood how the nervous system functions,” he says. His latest brain imaging study of 30 volunteers who had needles placed in their feet indicates that the signals reach centres in the brain called the thalamus and cingulate gyrus as well as reaching parts that are to do with the feet.
These areas are thought to be important for determining how we perceive pain. Endorphins work by blocking pain at the spinal cord level, preventing further signals from the injured area reaching the brain, but Cho’s work suggests that acupuncture might switch off pain perception in the brain itself.
However promising the mechanistic studies are, acupuncture still needs to prove itself clinically. Studies that have tried to explain the placebo effect find that placebos can tap into the endorphin system too, and can be blocked by naloxone. And believing in something can activate the brain directly too. So are these promising mechanisms really just showing us a promising placebo?
Adrian White, an acupuncture researcher and clinical trials expert from the University of Exeter, says this doesn’t mean we should give up on the technique. Part of the problem might lie with the difficulties of designing a trial that achieves the gold-standard of testing against a placebo, when neither patient nor doctor is aware of the treatment given. Other difficulties are inconsistencies in whether a Western or Eastern diagnosis was made, variations in the choice of acupoints chosen, and that trials don’t last anywhere near as long as a traditional course of treatment. As Jeanette Ezzo, an epidemiologist at the National Breast Cancer Coalition in Baltimore, points out: “You could throw away 95 per cent of the studies because they are all so poorly designed and much too small.”
A new placebo needle is going to change all that, White claims. The needle has a blunt end and a plastic tube around the shaft which holds it on the skin, but the needle never goes in. “Now we have a true placebo, just like a sugar pill in drug trials,” he says. The drawback is it will only work on acupuncture virgins. “As long as we have a supply of those we’re OK,” says White.
Perhaps just as important as the placebo needle is the therapeutic setting. Not only have we taken acupuncture out of the East, but we have taken the East out of acupuncture. By restoring some of the Eastern exoticism – herbs and needles at points for symptoms other than the main complaint, if you’re feeling tired, for example – the ancient needling technique might show its worth under the scrutiny of Western clinical trials. Lao believes in this holistic approach and includes a traditional diagnosis and herbs with his acupuncture treatment. Lao’s sterile clinic still lacks one crucial element of Chinese medicine, however: atmosphere. “Chinese people living in America who want the authentic treatment go to China town,” says Lao, “not the clinic.”