Acupuncture is a traditional Chinese therapy based on sticking needles into the dermis at precise points. Acupuncture is often described as "gateway woo" because of the increasing number of scientists and medical centers accepting it as respectable treatment.
While many doctors don't believe in chi or meridians, it is widely believed that acupuncture is more effective than randomly stabbing someone with needles while telling them it helps, despite a serious lack of randomized clinical trials. This belief is apparently because needles have less of a "magic" vibe than other forms of woo. Despite wasting good money, acupuncture researchers have yet to show consistent, statistically significant, and relevant effects in proper clinical trials.
Its theoretical basis is that health and sickness are caused by the good or bad flow of chi through the body, in particular along the twelve major meridians of the body (though some authorities list fourteen or even more) which run from head to toe along the body, and which are associated with the bladder, gallbladder, heart, large intestine, small intestine, kidneys, liver, lungs, spleen, stomach, pericardium, and "triple heater". It is necessary to translate this last term word for word from the Chinese because there is no such thing as the "triple heater".
The acupuncturist treats the ailments of these various parts by inserting needles at points lying on these meridians, known simply as "acupuncture points" and manipulating the needles to increase or decrease the flow of chi along that meridian.
Variants on acupuncture include auricular acupuncture, which involves sticking needles into particular parts of the outer ear, which supposedly correspond to different body parts (essentially reflexology with ears instead of feet); electroacupuncture, in which the needle carries a small electric current; and moxibustion, in which moxa (the plant commonly known as mugwort, Artemesia vulgaris) is set smouldering on the appropriate acupuncture point. Acupuncture can also be used to perform bloodletting. This is supposed to be good for a long list of unrelated diseases. Despite the fact that this is obviously very effective, Chinese bloodletting is banned in California.
Unlike many remedies which appeal to the New Age, acupuncture is genuinely pre-scientific and genuinely Asian. The earliest surviving text dealing with acupuncture is the Chinese text The Yellow Emperor's Classic of Internal Medicine, dating from about 300 BCE, well before any scientific understanding of disease, including germ theory, cell theory, and basic biology.
Acupuncture lost ground in China from the seventeenth century onwards, with the introduction of Western scientific ideas. It regained some of its prestige during the Cultural Revolution of the 1960s and 70s, and is widely practiced in modern China. It became popular in the West from the 1960s onwards.
Although the basics of acupuncture have remained the same since ancient times, the system has suffered the inevitable mutations and accretions: the original system, for example, had 365 acupuncture points; some modern systems catalog as many as 2000. There is no science to support even one point, and inventing more of them just gets more patients to pay money.
Sticking needles into people can cause the release into the bloodstream of endorphins and natural steroids such as cortisol. The medical version of this is called intramuscular stimulation and is of some use in the management of chronic pain. Acupuncture, to the extent it works, seems to do so in this manner. The pain relief from acupuncture seems to be mediated solely through the release of endorphins, as any perceived analgesic effect is reduced or eliminated when the patient has been pretreated with an opioid antagonist such as naloxone. However, the few supposed studies that show efficacy have been criticized for poor design, poor analysis and poor results. In fact, if acupuncture were held to the same standards as all other medications and drugs, the poor quality of the studies would have prevented it from ever being approved for use by the FDA.
As to the wider claims of acupuncturists, it seems on the face of it unlikely, given the unscientific basis of their claims, that they can have much effect on a patient's physiology by manipulating the flow of a non-existent substance around imaginary meridians. JREF noted that in studies using "no needles vs needles," the methodology of the study is an important consideration. 
However, a recent study using an MRI to view brain activity during an acupuncture session found that specific acupuncture points have distinct effects on cerebral activity in specific areas that are not otherwise predictable anatomically.
It is noticeable that acupuncturists tend chiefly to advertise their abilities to treat precisely those ailments which are chronic but intermittently better or worse (headaches, acne), or which have a strong psychosomatic element (impotence, asthma), or which are guaranteed to clear up rapidly anyway (the common cold), and are therefore are profiting from the placebo effect and regression to the mean.
It has also been found that far from curing disease, acupuncture has been a transmission agent for hepatitis C, MRSA, Staphylococcus aureus and acupuncture mycobacteriosis.
Acupressure is acupuncture without the needles.
Acupressure is part of the Western bundle of hypotheses and practices known as Traditional Chinese Medicine. You press on acupuncture pressure points to affect the meridian system and bring about relief by rebalancing yin, yang and qi. Apparently.
Considering the needles are the one bit of acupuncture that appears to do anything at all, with the rest of the theory being woo, acupressure is, unsurprisingly, not much good. Studies show possible effects, such as interaction with the body's pain reduction systems, but at a level that is not statistically significant. Studies are ongoing.
 See also
- ↑ http://scienceblogs.com/insolence/2008/11/thatll_teach_em_for_using_an_actual_vali.php
- ↑ "The best conclusion we can make today, based on all available evidence, is that acupuncture adds nothing to the non-specific effects of the attention from the practitioner." Acupuncture for Migraine
- ↑ Bleeding Peripheral Points: An Acupuncture Technique
- ↑ California Forbids Chinese Bloodletting, Ben Kavoussi, Science-Based Medicine, December 16, 2010.
- ↑ "Interaction of diazepam and naloxone on acupuncture induced pain relief" - Eriksson SV, Lundeberg T, Lundeberg S. 1991
- ↑ Another overhyped acupuncture study misinterpreted
- ↑ "In summary, Ernst et al. have shown that the evidence for efficacy of acupuncture for the treatment of pain is questionable, to say the least, and of particular concern is that its use can be dangerous. If the 57 systematic reviews they surveyed had been for a prescription drug and a similar list of serious adverse effects had been reported for that drug, we would hesitate to prescribe that drug. Is there any reason not to hold acupuncture to the same standards?" Acupuncture revisited
- ↑ 
- ↑ http://ecam.oxfordjournals.org/cgi/content/full/2/3/315
- ↑ Probably unwittingly so.
- ↑ British Medical Journal: Acupuncture transmitted infections, (Patrick Woo [sic] et al.) - BMJ 2010; 340:c1268
- ↑ http://consensus.nih.gov/1997/1997Acupuncture107html.htm NIH Consensus Development Program (3–5 November 1997). "Acupuncture --Consensus Development Conference Statement". National Institutes of Health.