Since its inception in 1895, chiropractic has been the subject of scientific research and criticism. Criticism has come both from philosophical conflicts within the profession and from critics outside it.
Conflicts within the profession comes from the differing schools of thought. Historically, the belief that a spinal joint dysfunction can interfere with the nervous system and result in many different conditions of diminished health, a concept known as vertebral subluxation, was one of the main assertions of chiropractic. Today, chiropractors place differing degrees of emphasis on subluxation, with some rejecting it entirely. While "straight" chiropractors hold a traditional view of subluxation, "mixer" chiropractors explain its importance in different terms, and the minority "reform" chiropractors reject it entirely. These different groups of chiropractors make different claims made about the effects of spinal adjustments, and of supplementing adjustments with additional treatments.
Chiropractic has been investigated by the scientific community. As a result of these inquiries, the chiropractic philosophy is evolving toward more scientific practices.
Chiropractic researchers Robert Mootz and Reed Phillips suggest that, in chiropractic's early years, influences from both straight and mixer concepts were incorporated into its construct. They conclude that chiropractic has both materialistic qualities that lend themselves to scientific investigation and vitalistic qualities that do not.
With relatively little federal funding, academic research in chiropractic has only recently become established in the USA. In 1994 and 1995, half of all grant funding to chiropractic researchers was from the US Health Resources and Services Administration (7 grants totaling $2.3 million). The Foundation for Chiropractic Education and Research (11 grants, $881,000) and the Consortium for Chiropractic Research (4 grants, $519,000) accounted for most of the rest. By 1997, there were 14 peer-reviewed chiropractic journals in English that encouraged the publication of chiropractic research, including The Journal of Manipulative and Physiological Therapeutics (JMPT), Topics in Clinical Chiropractic, and the Journal of Chiropractic Humanities. However, of these, only JMPT is included in Index Medicus. Research into chiropractic, whether from Universities or chiropractic colleges, is however often published in many other scientific journals.
While there is still debate about the effectiveness of chiropractic for the many conditions in which it is applied, chiropractic seems to be most effective for acute low back pain and tension headaches. When testing the efficacy of health treatments, double blind studies are considered acceptable scientific rigor. These are designed so that neither the patient nor the doctor knows whether they are using the actual treatment or a placebo (or "sham") treatment. However, chiropractic treatment involves a manipulation; "sham" procedures cannot be easily devised for this, and even if the patient is unaware whether the treatment is a real or sham procedure, the doctor cannot be unaware. Thus there may be "observer bias" - the tendency to see what you expect to see, and the potential for the patient to wish to report benefits to "please" the doctor. Similarly, it is often difficult to devise a sham procedure for surgical procedures, but it is not impossible. It is also a problem in evaluating treatments; even when there are objective outcome measures, the placebo effect can be very substantial. Thus, DCs have historically relied mostly on their own clinical experience and the shared experience of their colleagues, as reported in case studies, to direct their treatment methods. In this, they are not different to the practice in much of conventional medicine. . Consequently there has been a call to increase qualitative research studies which can better examine the whole chiropractic clinical encouter.
There is evidence that spinal manipulation is effective for the treatment of acute low back pain, tension headaches and some musculoskeletal issues, but not all studies support this conclusion. A systematic review of systematic reviews in 2006 by Edzard Ernst and P.H. Canter concluded that no data "demonstrate that spinal manipulation is an effective intervention for any condition. Given the possibility of adverse effects, this review does not suggest that spinal manipulation is a recommendable treatment." In 2007, Ernst performed another review, drawing similar findings which concluded: "Spinal manipulation, particularly when performed on the upper spine, is frequently associated with mild to moderate adverse effects. It can also result in serious complications such as vertebral artery dissection followed by stroke. Currently, the incidence of such events is not known. In the interest of patient safety we should reconsider our policy towards the routine use of spinal manipulation." A commentary from a chiropractic and osteopathic journal disputed Ernst and Canter's conclusion as, "..definitely not based on an acceptable quality review of systematic reviews and should be interpreted very critically by the scientific community, clinicians, patients, and health policy makers. Their conclusions are certainly not valid enough to discredit the large body of professionals utilizing spinal manipulation."
One controlled trial showed a lowering of blood pressure in hypertensive patients similar to taking two blood-pressure lowering drugs at once after alignment of the atlas vertebra.
Sociologist Leslie Biggs interviewed 600 Canadian DCs in 1997: while 86% felt that chiropractic methods needed to be validated, 74% did not believe that controlled clinical trials were the best way to evaluate chiropractic. Moreover, 68% believed that "most diseases are caused by spinal malalignment", although only 30% agreed that "subluxation was the cause of many diseases".
Even when a valid mechanism of action is not determined, it is generally thought sufficient to present evidence showing benefit for the claims made. There is wide agreement that, where applicable, an evidence based medicine framework should be used to assess health outcomes, and that systematic reviews with strict protocols are important for objectively evaluating treatments. Where evidence from such reviews is lacking, this does not necessarily mean that the treatment is ineffective, only that the case for a benefit of treatment may not have been rigorously established.
A 2005 editorial in JMPT, "The Cochrane Collaboration: is it relevant for doctors of chiropractic?" proposed that involvement in Cochrane collaboration would be a way for chiropractic to gain greater acceptance within medicine. The collaboration has 11,500 contributors from more than 90 countries organized in 50 review groups. For chiropractic, relevant review groups include the Back Group; the Bone, Joint, and Muscle Trauma Group; the Musculoskeletal Group; and the Neuromuscular Disease Group. The editorial states that, for example, "a chiropractor may provide conservative care supported by a Cochrane review to a patient with carpal tunnel syndrome. If the patient's symptoms become progressive, the doctor may consider referring the patient for surgery using a recent Cochrane review that examined new surgical techniques compared with traditional open surgery..."
The Cochrane Collaboration did not find enough evidence to support or refute the claim that manual therapy (including, but not limited to, chiropractic) is beneficial for asthma. Carpal tunnel syndrome trials have not shown benefit from diuretics, non-steroidal anti-inflammatory drugs, magnets, laser acupuncture, exercise or chiropractic and there is not enough evidence to show the effects of spinal manipulation (including, but not limited to, chiropractic) for painful menstrual periods. Bandolier found limited evidence that spinal manipulative therapy (including, but not limited to, chiropractic) might reduce the frequency and intensity of migraine attacks, but the evidence that spinal manipulation is better than amitriptyline, or adds to the effects of amitriptyline, is insubstantial for the treatment of migraine, although "spinal manipulative therapy might be worth trying for some patients with migraine or tension headaches."
According to Bandolier, a systematic review of a small, poor quality set of trials provided no convincing evidence for long-term benefits of chiropractic interventions for acute or chronic low back pain, despite some positive overall findings but there might be some short-term pain relief, especially in patients with acute pain. However, the BMJ noted in a study on long-term low-back problems "...improvement in all patients at three years was about 29% more in those treated by chiropractors than in those treated by the hospitals. The beneficial effect of chiropractic on pain was particularly clear." A 1994 study by the U.S. Agency for Health Care Policy and Research (AHCPR) and the U.S. Department of Health and Human Services endorses spinal manipulation for acute low back pain in adults in its Clinical Practice Guideline.
The first significant recognition of the appropriateness of spinal manipulation for low back pain was performed by the RAND Corporation. This meta-analysis concluded that some forms of spinal manipulation were successful in treating certain types of lower back pain. Some chiropractors claimed these results as proof of chiropractic hypotheses, but RAND's studies were about spinal manipulation, not chiropractic specifically, and dealt with appropriateness, which is a measure of net benefit and harms; the efficacy of chiropractic and other treatments were not explicitly compared. In 1993, Dr Shekelle rebuked some DCs for their exaggerated claims: ...we have become aware of numerous instances where our results have been seriously misrepresented by chiropractors writing for their local paper or writing letters to the editor....
There is conflict in the results of chiropractic research. For instance, many DCs claim to treat infantile colic. According to a 1999 survey, 46% of chiropractors in Ontario treated children for colic. In 1999 a Danish randomized controlled clinical trial with a blinded observer suggested that there is evidence that spinal manipulation might help infantile colic. However, in 2001, a Norwegian blinded study concluded that chiropractic spinal manipulation was no more effective than placebo for treating infantile colic.
In 1997, historian Joseph Keating Jr described chiropractic as a "science, antiscience and pseudoscience", and said "Although available scientific data support chiropractic's principle intervention method (the manipulation of patients with lower back pain), the doubting, skeptical attitudes of science do not predominate in chiropractic education or among practitioners". He argued that chiropractic's culture has nurtured antiscientific attitudes and activities, and that "a combination of uncritical rationalism and uncritical empiricism has been bolstered by the proliferation of pseudoscience journals of chiropractic wherein poor quality research and exuberant over-interpretation of results masquerade as science and provide false confidence about the value of various chiropractic techniques". However, in 1998, after reviewing the articles published in the JMPT from 1989-1996, he concluded, :"substantial increases in scholarly activities within the chiropractic profession are suggested by the growth in scholarly products published in the discipline's most distinguished periodical (JMPT). Increases in controlled outcome studies, collaboration among chiropractic institutions, contributions from nonchiropractors, contributions from nonchiropractic institutions and funding for research suggest a degree of professional maturation and growing interest in the content of the discipline."
Joseph C. Keating, Jr. and researchers argued: "The dogma of subluxation is perhaps the greatest single barrier to professional development for chiropractors. It skews the practice of the art in directions that bring ridicule from the scientific community and uncertainty among the public. Failure to challenge subluxation dogma perpetuates a marketing tradition that inevitably prompts charges of quackery. Subluxation dogma leads to legal and political strategies that may amount to a house of cards and warp the profession's sense of self and of mission. Commitment to this dogma undermines the motivation for scientific investigation of subluxation as hypothesis, and so perpetuates the cycle."
Dr. Craig F. Nelson states, "The chiropractic profession has crusaded against one of the most effective public health measures of all time¬vaccination¬and many of its members publicly scoff at the germ theory of disease. Even today some chiropractors are openly opposed to vaccination. Some practice "muscle testing"¬for example, manually, subjectively appraising the muscle strength of a patient with a vitamin pill in his or her hand as a means of diagnosing nutritional deficiencies."
Reports and studies The Manga Report
The Manga Report was an outcomes-study funded by the Ontario Ministry of Health and conducted by three health economists led by Professor Pran Manga. The Report supported the scientific validity, safety, efficacy, and cost-effectiveness of chiropractic for low-back pain, and found that chiropractic care had higher patient satisfaction levels than conventional alternatives. The report states that "The literature clearly and consistently shows that the major savings from chiropractic management come from fewer and lower costs of auxiliary services, fewer hospitalizations, and a highly significant reduction in chronic problems, as well as in levels and duration of disability."
Workers' Compensation studies
In 1998, a study of 10,652 Florida workers' compensation cases was conducted by Steve Wolk. He concluded that "a claimant with a back-related injury, when initially treated by a chiropractor versus a medical doctor, is less likely to become temporarily disabled, or if disabled, remains disabled for a shorter period of time; and claimants treated by medical doctors were hospitalized at a much higher rate than claimants treated by chiropractors." Similarly, a 1991 study of Oregon Workers' Compensation Claims examined 201 randomly selected workers' compensation cases that involved disabling low-back injuries: when individuals with similar injuries were compared, those who visited DCs generally missed fewer days of work than those who visited MDs.
A 1989 study analyzed data on Iowa state records from individuals who filed claims for back or neck injuries. The study compared benefits and the cost of care from MDs, DCs and DOs, focusing on individuals who had missed days of work and who had received compensation for their injuries. Individuals who visited DCs missed on average 2.3 fewer days than those who visited MDs, and 3.8 fewer days than those who saw DOs, and accordingly, less money was dispersed as employment compensation on average for individuals who visited DCs.
In 1989, a survey by Cherkin et al. concluded that patients receiving care from health maintenance organizations in the state of Washington were three times as likely to report satisfaction with care from DCs as they were with care from other physicians. The patients were also more likely to believe that their chiropractor was concerned about them.
American Medical Association (AMA)
In 1997, the following statement was adopted as policy of the AMA after a report on a number of alternative therapies.
Specifically about chiropractic it said, :"Manipulation has been shown to have a reasonably good degree of efficacy in ameliorating back pain, headache, and similar musculoskeletal complaints." In 1992, the AMA issued this statement: :"It is ethical for a physician to associate professionally with chiropractors provided that the physician believes that such association is in the best interests of his or her patient. A physician may refer a patient for diagnostic or therapeutic services to a chiropractor permitted by law to furnish such services whenever the physician believes that this may benefit his or her patient. Physicians may also ethically teach in recognized schools of chiropractic. (V, VI)"
British Medical Association
The British Medical Association notes that "There is also no problem with GPs referring patients to practitioners in osteopathy and chiropractic who are registered with the relevant statutory regulatory bodies, as a similar means of redress is available to the patient."
WebMD has published several studies regarding chiropractic adjustments. The first of these, published on October 11, 2004 in the Archives of Internal Medicine, concluded that chiropractic cut the cost of treating back pain by 28%, reduced hospitilizations by 41%, back surgeries by 32%, and the cost of medical imaging, such as X-rays or MRIs, by 37%. Researchers did not look at patient satisfaction in this study, but study co-leader Douglas Metz says company studies show that 95% of chiropractic care patients are satisfied with the care they receive.
Critics of chiropractic have labeled it pseudoscience and have expressed doubt that its methods can be effective by any mechanism other than placebo.
In the Encyclopedia of Pseudoscience, William F. Williams asserts that vitalism - the philosophy that human functions are not entirely due to physicochemical forces, but rather to more abstract "vital forces" - "form the basis for many pseudoscientific health systems." Williams accuses vitalists of rejecting the scientific method in favor of subjective experience.
Quackwatch is even more critical of chiropractic; its founder, Stephen Barrett, has written that it is "absurd" to think that chiropractors are qualified to be primary care providers.
William T. Jarvis, Ph.D. stated: "Chiropractic is a controversial health-care system that has been legalized throughout the United States and in several other countries. In the United States in 1984, roughly 10.7 million people made 163 million office visits to 30,000 chiropractors. More than three fourths of the states require insurance companies to include chiropractic services in health and accident policies. The federal government pays for limited chiropractic services under Medicare, Medicaid, and its vocational rehabilitation program, and the Internal Revenue Service allows a medical deduction for chiropractic services. Chiropractors cite such facts as evidence of "recognition." However, these are merely business statistics and legal arrangements that have nothing to do with chiropractic's scientific validity."
Lon Morgan, DC, a reform chiropractor, expressed his view of Innate Intelligence this way: "Innate Intelligence clearly has its origins in borrowed mystical and occult practices of a bygone era. It remains untestable and unverifiable and has an unacceptably high penalty/benefit ratio for the chiropractic profession. The chiropractic concept of Innate Intelligence is an anachronistic holdover from a time when insufficient scientific understanding existed to explain human physiological processes. It is clearly religious in nature and must be considered harmful to normal scientific activity."