Chiropractic is a health care approach and profession that emphasizes diagnosis, treatment and prevention of mechanical disorders of the musculoskeletal system, especially the spine, under the hypothesis that these disorders affect general health via the nervous system.[1] It is generally considered to be complementary and alternative medicine,[2] a characterization that many chiropractors reject.[3] The main treatment involves manual therapy including manipulation of the spine, other joints, and soft tissue; treatment also includes exercises and health and lifestyle counseling.[4] Traditionally, chiropractic assumes that a vertebral subluxation or spinal joint dysfunction interferes with the body's function and its innate intelligence,[5] a notion that brings ridicule from mainstream science and medicine.[6]
D.D. Palmer founded chiropractic in the 1890s and his son B.J. Palmer helped to expand it in the early 20th century.[7] It has two main groups: "straights", now the minority, emphasize vitalism, innate intelligence and spinal adjustments, and consider subluxations to be the leading cause of all disease; "mixers" are more open to mainstream and alternative medical techniques such as exercise, massage, nutritional supplements, and acupuncture.[8] Chiropractic is well established in the U.S., Canada and Australia.[9]
For most of its existence, chiropractic has battled with mainstream medicine, sustained by ideas such as subluxation[10] that are not based on solid science.[11] Vaccination remains controversial among chiropractors.[12] The American Medical Association called chiropractic an "unscientific cult"[13] and boycotted it until losing a 1987 antitrust case.[14] Chiropractic has had a strong political base and sustained demand for services; in recent decades, it has gained more legitimacy and greater acceptance among medical physicians and health plans,[14] and evidence-based medicine has been used to review research studies and generate practice guidelines.[15] Many studies of treatments used by chiropractors have been conducted, with conflicting results. Collectively, systematic reviews of this research have not demonstrated that spinal manipulation is effective, with the possible exception of treatment of back pain.[11] The efficacy and cost-effectiveness of maintenance chiropractic care are unknown.[16] Although spinal manipulation can have serious complications in rare cases,[17][18] chiropractic care is generally safe when employed skillfully and appropriately.[19]
Chiropractic's early philosophy was rooted in vitalism, spiritual inspiration and rationalism. A philosophy based on deduction from irrefutable doctrine helped distinguish chiropractic from medicine, provided it with legal and political defenses against claims of practicing medicine without a license, and allowed chiropractors to establish themselves as an autonomous profession. This "straight" philosophy, taught to generations of chiropractors, rejects the inferential reasoning of the scientific method,[21] and relies on deductions from vitalistic first principles rather than on the materialism of science.[20] However, most practitioners currently accept the importance of scientific research into chiropractic,[21] and most practitioners are "mixers" who attempt to combine the materialistic reductionism of science with the metaphysics of their predecessors and with the holistic paradigm of wellness;[20] a 2008 commentary proposed that chiropractic actively divorce itself from the straight philosophy as part of a campaign to eliminate untestable dogma and engage in critical thinking and evidence-based research.[22]
Although a wide diversity of ideas currently exists among chiropractors,[21] they share the belief that the spine and health are related in a fundamental way, and that this relationship is mediated through the nervous system.[23] Chiropractors study the biomechanics, structure and function of the spine, along with what they say are its effects on the musculoskeletal and nervous systems and its role in health and disease.[24]
Chiropractic philosophy includes the following perspectives:[20]
Chiropractic is often described as two professions masquerading as one. Unlike the distinction between podiatry (a science-based profession for foot disorders) and foot reflexology (an unscientific philosophy which posits that many disorders arise from the feet), in chiropractic the two professions attempt to live under one roof.[22]
Straight chiropractors adhere to the philosophical principles set forth by D.D. and B.J. Palmer, and retain metaphysical definitions and vitalistic qualities. Straight chiropractors believe that vertebral subluxation leads to interference with an "Innate Intelligence" exerted via the human nervous system and is a primary underlying risk factor for almost any disease. Straights view the medical diagnosis of patient complaints (which they consider to be the "secondary effects" of subluxations) to be unnecessary for chiropractic treatment. Thus, straight chiropractors are concerned primarily with the detection and correction of vertebral subluxation via adjustment and do not "mix" other types of therapies.[26] Their philosophy and explanations are metaphysical in nature and prefer to use traditional chiropractic lexicon (i.e. perform spinal analysis, detect subluxation, correct with adjustment, etc.). They prefer to remain separate and distinct from mainstream health care.
Mixer chiropractors "mix" diagnostic and treatment approaches from osteopathic, medical, and chiropractic viewpoints. Unlike straight chiropractors, mixers believe subluxation is one of many causes of disease, and they incorporate mainstream medical diagnostics and employ many treatments including conventional techniques of physical therapy such as exercise, massage, ice packs, and moist heat, along with nutritional supplements, acupuncture, homeopathy, herbal remedies, and biofeedback. Mixers tend to be open to mainstream medicine and are the majority group.[8]
Palmer hypothesized that vertebral joint misalignments, which he termed vertebral subluxations, interfered with the body's function and its inborn (innate) ability to heal itself.[5] D.D. Palmer repudiated his earlier theory that vertebral subluxations caused pinched nerves in the intervertebral spaces in favor of subluxations causing altered nerve vibration, either too tense or too slack, affecting the tone (health) of the end organ. D.D. Palmer, using a vitalistic approach, imbued the term subluxation with a metaphysical and philosophical meaning. He qualified this by noting that knowledge of innate intelligence was not essential to the competent practice of chiropractic.[27] This concept was later expanded upon by his son, B.J. Palmer and was instrumental in providing the legal basis of differentiating chiropractic medicine from conventional medicine. In 1910, D.D. Palmer theorized that the nervous system controlled health:
The concept of subluxation remains unsubstantiated and largely untested, and a debate about whether to keep it in the chiropractic paradigm has been ongoing for decades.[6] In general, critics of traditional subluxation-based chiropractic (including chiropractors) are skeptical of its clinical value, dogmatic beliefs and metaphysical approach. While straight chiropractic still retains the traditional vitalistic construct espoused by the founders, evidence-based chiropractic suggests that a mechanistic view will allow chiropractic care to become integrated into the wider health care community.[6] This is still a continuing source of debate within the chiropractic profession as well, with some schools of chiropractic still teaching the traditional/straight subluxation-based chiropractic, while others have moved towards an evidence-based chiropractic that rejects metaphysical foundings and limits itself to primarily neuromusculoskeletal conditions.[29][30]
A 2003 survey of North American chiropractors found that 88% wanted to retain the term vertebral subluxation complex, and that when asked to estimate the percent of disorders of internal organs (such as the heart, the lungs, or the stomach) that subluxation significantly contributes to, the mean response was 62%.[31] In 2005, subluxation was defined by the World Health Organization as "a lesion or dysfunction in a joint or motion segment in which alignment, movement integrity and/or physiological function are altered, although contact between joint surfaces remains intact. It is essentially a functional entity, which may influence biomechanical and neural integrity." This differs from the medical definition of subluxation as a significant structural displacement, which can be seen with static imaging techniques such as X-rays.[19] Attorney David Chapman-Smith, Secretary-General of the World Federation of Chiropractic, has stated that "subluxations are not structural entities and cannot be detected on x‑ray."[32]
Chiropractors, also known as doctors of chiropractic or chiropractic physicians in many jurisdictions,[33] emphasize the conservative management of the neuromusculoskeletal system without the use of medicines or surgery,[19] with special emphasis on the spine.[1] Chiropractic combines aspects from mainstream and alternative medicine: although chiropractors have many attributes of primary care providers, chiropractic has more of the attributes of a medical specialty like dentistry or podiatry.[34] It has been proposed that chiropractors specialize in nonsurgical spine care, instead of attempting to also treat other problems,[22][34] but the more expansive view of chiropractic is still widespread.[35] Mainstream health care and governmental organizations such as the World Health Organization consider chiropractic to be complementary and alternative medicine (CAM);[2] however, a 2008 study reported that 31% of surveyed chiropractors categorized chiropractic as CAM, 27% as integrated medicine, and 12% as mainstream medicine.[3]
The practice of chiropractic medicine involves a range of diagnostic methods including skeletal imaging, observational and tactile assessments, and orthopedic and neurological evaluation.[19] A chiropractor may also refer a patient to an appropriate specialist, or co-manage with another health care provider.[34] Common patient management involves spinal manipulation (SM) and other manual therapies to the joints and soft tissues, rehabilitative exercises, health promotion, electrical modalities, complementary procedures, and lifestyle counseling.[4]
Chiropractors cannot write medical prescriptions or perform major surgery. In the U.S. their scope of practice varies by state in areas such as conducting laboratory tests or diagnostic procedures, dispensing dietary supplements, and using other therapies such as homeopathy and acupuncture; in the state of Oregon they can become certified to perform minor surgery and to deliver children via natural childbirth.[36] A 2003 survey of North American chiropractors found that a slight majority favored allowing them to write prescriptions for over-the-counter drugs.[31] A related field, veterinary chiropractic, applies manual therapies to animals and is recognized in a few U.S. states,[37] but is not recognized by the American Chiropractic Association as being chiropractic.[38]
Chiropractic overlaps with several other manual-therapy professions, including massage therapy, osteopathy, and physical therapy.[39] Chiropractic is autonomous and competitive with mainstream medicine[40] and osteopathy outside the U.S. remains primarily a manual medical system;[41] physical therapists work alongside and cooperate with mainstream medicine, and osteopathic medicine in the U.S. has merged with the medical profession.[40] Members distinguish these competing professions with rhetorical strategies that include claims that, compared to other professions, chiropractors heavily emphasize spinal manipulation, tend to use firmer manipulative techniques, and promote maintenance care; that osteopaths use a wider variety of treatment procedures; and that physical therapists emphasize machinery and exercise.[39]
No single profession "owns" spinal manipulation and there is little consensus as to which profession should administer SM, raising concerns by chiropractors that orthodox medical physicians could "steal" SM procedures from chiropractors. A focus on evidence-based SM research has also raised concerns that the resulting practice guidelines could limit the scope of chiropractic practice to treating backs and necks.[15] Some U.S. states prohibit physical therapists from performing SM, some states allow them to do it only if they have completed chiropractic training, and some states allow only chiropractors to perform SM, or only chiropractors and physicians. Bills to further prohibit non-chiropractors from performing SM are regularly introduced into state legislatures and are opposed by physical therapist organizations.[42]
Spinal manipulation, which chiropractors call "spinal adjustment" or "chiropractic adjustment", is the most common treatment used in chiropractic care;[43] in the U.S., chiropractors perform over 90% of all manipulative treatments.[44] Spinal manipulation is a passive manual maneuver during which a three-joint complex is taken past the normal range of movement, but not so far as to dislocate or damage the joint; its defining factor is a dynamic thrust, which is a sudden force that causes an audible release and attempts to increase a joint's range of motion. More generally, spinal manipulative therapy (SMT) describes techniques where the hands are used to manipulate, massage, mobilize, adjust, stimulate, apply traction to, or otherwise influence the spine and related tissues; in chiropractic care SMT most commonly takes the form of spinal manipulation.[45]
There are several schools of chiropractic adjustive techniques, although most chiropractors mix techniques from several schools. The following adjustive procedures were received by more than 20% of patients of licensed U.S. chiropractors in a 2003 survey:[43] Diversified technique (full-spine manipulation), extremity adjusting, Activator technique (which uses a spring loaded tool to deliver precise adjustments to the spine), Thompson Technique, Gonstead (which looks at the whole spine with the philosophy that a vertebral misalignment may affect other areas of the spine, emphasizing the mechanical aspects of the spine), Cox/flexion-distraction (a gentle, non-force adjusting procedure which mixes chiropractic principles with osteopathic principles and utilizes specialized adjusting tables with movable parts), adjustive instrument, Sacro-Occipital Technique (which models the spine as a torsion bar), Nimmo Receptor-Tonus Technique, and Applied Kinesiology (which emphasises "muscle testing" as a diagnostic tool).[46] Medicine-assisted manipulation, such as manipulation under anesthesia, involves sedation or local anesthetic and is done by a team that includes an anesthesiologist; a 2008 systematic review did not find enough evidence to make recommendations about its use for chronic low back pain.[47]
Many other procedures are used by chiropractors for treating the spine, other joints and tissues, and general health issues. The following procedures were received by more than 1/3 of patients of licensed U.S. chiropractors in a 2003 survey: Diversified technique (full-spine manipulation; mentioned in previous paragraph), physical fitness/exercise promotion, corrective or therapeutic exercise, ergonomic/postural advice, self-care strategies, activities of daily living, changing risky/unhealthy behaviors, nutritional/dietary recommendations, relaxation/stress reduction recommendations, ice pack/cryotherapy, extremity adjusting (also mentioned in previous paragraph), trigger point therapy, and disease prevention/early screening advice.[43]
Chiropractors obtain a first professional degree in the field of chiropractic.[48] In the United States, 90 semester hours or about two years of undergraduate education are pre-requisite for entrance to chiropractic school.[citation needed] Canada requires a minimum three years of undergraduate education as a prerequisite for chiropractic school, and at least 4200 instructional hours (or the equivalent) of full‐time chiropractic education for matriculation through an accredited chiropractic program.[49] The World Health Organization (WHO) guidelines suggest three major full-time educational paths culminating in either a DC, DCM, BSc, or MSc degree. Besides the full-time paths, they also suggest a conversion program for people with other health care education and limited training programs for regions where no legislation governs chiropractic.[19]
Upon graduation, there may be a requirement to pass national, state, or provincial board examinations before being licensed to practice in a particular jurisdiction.[50][51] Depending on the location, continuing education may be required to renew these licenses.[52][53] Specialty training is available through part-time postgraduate education programs such as chiropractic orthopedics and sports chiropractic, and through full-time residency programs such as radiology or orthopedics.[54]
Chiropractic is established in the U.S., Canada, and Australia, and is present to a lesser extent in many other countries.[9] In the U.S., chiropractic schools are accredited through the Council on Chiropractic Education (CCE) while the General Chiropractic Council (GCC) is the statutory governmental body responsible for the regulation of chiropractic in the UK.[55][56] CCEs in the U.S., Canada, Australia and Europe have joined to form CCE-International (CCE-I) as a model of accreditation standards with the goal of having credentials portable internationally.[57] Today, there are 18 accredited Doctor of Chiropractic programs in the U.S.,[58] 2 in Canada,[59] 6 in Australasia,[60] and 4 in Europe.[61] All but one of the chiropractic colleges in the U.S. are privately funded, but in several other countries they are in government-sponsored universities and colleges.[62]
Regulatory colleges and chiropractic boards in the U.S., Canada, and Australia are responsible for protecting the public, standards of practice, disciplinary issues, quality assurance and maintenance of competency.[63][64] There are an estimated 53,000 chiropractors in the U.S. (2006),[65] 7,000 in Canada (2009),[66] 2,500 in Australia (2000),[67] and 1,500 in the UK (2000).[68]
A 2008 commentary proposed that the chiropractic profession actively regulate itself to combat abuse, fraud, and quackery, which are more prevalent in chiropractic than in other health care professions, violating the social contract between patients and physicians.[22] Unsubstantiated claims about the efficacy of chiropractic have continued to be made by individual chiropractors and chiropractic associations.[11] The largest chiropractic associations in the U.S. and Canada distributed patient brochures which contained unsubstantiated claims.[69] Chiropractors, especially in America, have a reputation for unnecessarily treating patients. In many circumstances the focus seems to be put on economics instead of health care.[70] Sustained chiropractic care is promoted as a preventative tool but unnecessary manipulation could possibly present a risk to patients. Some chiropractors are concerned by the routine unjustified claims chiropractors have made.[11] A study of California disciplinary statistics during 1997–2000 reported 4.5 disciplinary actions per 1000 chiropractors per year, compared to 2.27 for MDs; the incident rate for fraud was 9 times greater among chiropractors (1.99 per 1000 chiropractors per year) than among MDs (0.20).[71]
In the U.S., chiropractic is the largest alternative medical profession,[8] and is the third largest doctored profession, behind medicine and dentistry.[72] The percentage of population that utilizes chiropractic care at any given time generally falls into a range from 6% to 12% in the U.S. and Canada,[73] with a global high of 20% in Alberta.[74] Chiropractors are the most common CAM providers for children and adolescents, who consume up to 14% of all visits to chiropractors.[75] The vast majority who seek chiropractic care do so for relief from back and neck pain and other neuromusculoskeletal complaints;[76] most do so specifically for low back pain. Practitioners such as chiropractors are often used as a complementary form of care to primary medical intervention.[73] Satisfaction rates are typically higher for chiropractic care compared to medical care, with a 1998 U.S. survey reporting 83% of persons satisfied or very satisfied with their care; quality of communication seems to be a consistent predictor of patient satisfaction with chiropractors.[77]
Chiropractic does not have the same level of mainstream credibility as other healthcare professions. Public perception of chiropractic compares unfavorably with mainstream medicine with regard to ethics and honesty: in a 2006 Gallup Poll of U.S. adults, chiropractors rated last among seven health care professions for being very high or high in honesty and ethical standards, with 36% of poll respondents rating chiropractors very high or high; the corresponding ratings for other professions ranged from 62% for dentists to 84% for nurses.[22][78][79]
Utilization of chiropractic care is sensitive to the costs incurred by the co-payment by the patient.[2] The use of chiropractic declined from 9.9% of U.S. adults in 1997 to 7.4% in 2002; this was the largest relative decrease among CAM professions, which overall had a stable use rate.[80] Employment of U.S. chiropractors is expected to increase 14% between 2006 and 2016, faster than the average for all occupations.[65]
In the U.S., most states require insurers to cover chiropractic care, and most HMOs cover these services.[75] In Canada, there is lack of coverage under the universal public health insurance system.[81] In Australia, most private health insurance funds cover chiropractic care, and the federal government funds chiropractic care when the patient is referred by a medical practitioner.[82]
Chiropractic was founded in the 1890s by Daniel David (D.D.) Palmer in Davenport, Iowa. Palmer, a magnetic healer, hypothesized that manual manipulation of the spine could cure disease. Chiropractic competed with its predecessor osteopathy, another medical system based on magnetic healing and founded by a charismatic midwesterner in opposition to conventional medicine; however, where osteopathic postulated improved blood flow via manipulation, chiropractic postulated improved neural transmissions.[83] Although initially keeping chiropractic a family secret, in 1898 Palmer began teaching it to a few students at his new Palmer School of Chiropractic. One student, his son Bartlett Joshua (B.J.) Palmer, became committed to promoting chiropractic, took over the Palmer School in 1906, and rapidly expanded its enrollment.[7] Prosecutions and incarcerations of chiropractors for practicing medicine without a license grew common, and to defend against medical statutes B.J. argued that chiropractic was separate and distinct from medicine, asserting that chiropractors "analyzed" rather than "diagnosed", and "adjusted" subluxations rather than "treated" disease.[26] Early chiropractors believed that all disease was caused by interruptions in the flow of innate intelligence, a vital nervous energy or life force that represented God's presence in man; chiropractic leaders often invoked religious imagery and moral traditions. D.D. and B.J. both seriously considered declaring chiropractic a religion, which might have provided legal protection under the U.S. constitution, but decided against it partly to avoid confusion with Christian Science.[7][84] Early chiropractors also tapped into the Populist movement, emphasizing craft, hard work, competition, and advertisement, aligning themselves with the common man against intellectuals and trusts, among which they included the American Medical Association (AMA).[7]
Chiropractic has seen considerable controversy and criticism. Although D.D. and B.J. were "straight" and disdained the use of instruments, some early chiropractors, whom B.J. scornfully called "mixers", advocated use of instruments. In 1910 B.J. changed course and endorsed X-rays as necessary for diagnosis; this resulted in a significant exodus from the Palmer School of the more conservative faculty and students. The mixer camp grew until by 1924 B.J. estimated that only 3,000 of the U.S.'s 25,000 chiropractors remained straight. That year, B.J.'s promotion of the neurocalometer, a new temperature-sensing device, was another sign of chiropractic's gradual acceptance of medical technology, although it was highly controversial among B.J.'s fellow straights. Despite heavy opposition by organized medicine, by the 1930s chiropractic was the largest alternative healing profession in the U.S.[7] The longstanding feud between chiropractors and medical doctors continued for decades. The AMA labeled chiropractic an "unscientific cult" in 1966,[13] and until 1980 held that it was unethical for medical doctors to associate with "unscientific practitioners".[85] This culminated in a landmark 1987 decision, Wilk v. AMA, in which the court found that the AMA had engaged in unreasonable restraint of trade and conspiracy, and which ended the AMA's de facto boycott of chiropractic.[14]
Serious research to test chiropractic theories did not begin until the 1970s, and is continuing to be hampered by what are characterized as antiscientific and pseudoscientific ideas that sustained the profession in its long battle with organized medicine. By the mid 1990s there was a growing scholarly interest in chiropractic, which helped efforts to improve service quality and establish clinical guidelines that recommended manual therapies for acute low back pain.[26] In recent decades chiropractic gained legitimacy and greater acceptance by medical physicians and health plans, and enjoyed a strong political base and sustained demand for services. However, its future seemed uncertain: as the number of practitioners grew, evidence-based medicine insisted on treatments with demonstrated value, managed care restricted payment, and competition grew from massage therapists and other health professions. The profession responded by marketing natural products and devices more aggressively, and by reaching deeper into alternative medicine and primary care.[14]
The principles of evidence-based medicine have been used to review research studies and generate practice guidelines outlining professional standards that specify which chiropractic treatments are legitimate and perhaps reimbursable under managed care.[15] Evidence-based guidelines are supported by one end of an ideological continuum among chiropractors; the other end employs what is considered by many chiropractic researchers to be antiscientific reasoning and unsubstantiated claims,[1][6][10][86] that have been called ethically suspect when they let practitioners maintain their beliefs to patients' detriment.[1] A 2007 survey of Alberta chiropractors found that they do not consistently apply research in practice, which may have resulted from a lack of research education and skills.[87] Evidence-based chiropractors possess the ability to apply research in practice. Continued education enhances the scientific knowledge of the practitioner.[88]
Opinions differ as to the efficacy of chiropractic treatment.[62] Many controlled clinical studies of spinal manipulation (SM) are available, but their results disagree,[89] and they are typically of low quality.[90] Health claims made by chiropractors about using manipulation for pediatric health conditions are supported by only low levels of scientific evidence[75][91] that does not demonstrate clinically relevant benefits.[92] A 2008 critical review found that with the possible exception of back pain, chiropractic SM has not been shown to be effective for any medical condition, and suggested that many guidelines recommend chiropractic care for low back pain because no therapy has been shown to make a real difference,[11] but a 2008 supportive review found serious flaws in the critical approach and found that SM and mobilization are at least as effective for chronic low back pain as other efficacious and commonly used treatments.[93] Most research has focused on spinal manipulation (SM) in general,[94] rather than solely on chiropractic SM.[15] A 2002 review of randomized clinical trials of SM[34] was criticized for not distinguishing between studies of SM in general, and studies on chiropractic SM in particular;[95] however the review's authors stated that they did not consider this difference to be a significant point as research on SM is equally useful regardless of which practitioner provides it.[94]
There is a wide range of ways to measure treatment outcomes.[96] Chiropractic care, like all medical treatment, benefits from the placebo response.[97] It is hard to construct a trustworthy placebo for clinical trials of spinal manipulative therapy (SMT), as experts often disagree about whether a proposed placebo actually has no effect.[98] The efficacy of maintenance care in chiropractic is unknown.[16]
Available evidence covers the following conditions:
Chiropractic care in general is safe when employed skillfully and appropriately. Manipulation is regarded as relatively safe, but as with all therapeutic interventions, complications can arise, and it has known adverse effects, risks and contraindications. Absolute contraindications to spinal manipulative therapy are conditions that should not be manipulated; these contraindications include rheumatoid arthritis and conditions known to result in unstable joints. Relative contraindications are conditions where increased risk is acceptable in some situations and where low-force and soft-tissue techniques are treatments of choice; these contraindications include osteoporosis.[19] Although most contraindications apply only to manipulation of the affected region, some neurological signs indicate referral to emergency medical services; these include sudden and severe headache or neck pain unlike that previously experienced.[18]
Spinal manipulation is associated with frequent, mild and temporary adverse effects,[17][18] including new or worsening pain or stiffness in the affected region.[123] They have been estimated to occur in 33% to 61% of patients, and frequently occur within an hour of treatment and disappear within 24 to 48 hours.[124] Rarely,[19] spinal manipulation, particularly on the upper spine, can also result in complications that can lead to permanent disability or death; these can occur in adults[17] and children.[125] Estimates vary widely for the incidence of these complications,[124] and the actual incidence is unknown, due to high levels of underreporting and to the difficulty of linking manipulation to adverse effects such as stroke, which is a particular concern.[17] Several case reports show temporal associations between interventions and potentially serious complications. Vertebrobasilar artery stroke is statistically associated with chiropractic services in persons under 45 years of age, but it is similarly associated with general practitioner services, suggesting that these associations are likely explained by preexisting conditions.[104][126] Weak to moderately strong evidence supports causation (as opposed to statistical association) between cervical manipulative therapy (whether chiropractic or not) and vertebrobasilar artery stroke.[127]
Chiropractors sometimes employ diagnostic imaging techniques such as X-rays and CT scans that rely on ionizing radiation; practice guidelines aim to reduce unnecessary radiation exposure,[128] which increase cancer risk in proportion to the amount of radiation received.[129]
A 2006 qualitative review found that the research literature suggests that chiropractic obtains at least comparable outcomes to alternatives with potential cost savings.[130] A 2006 systematic cost-effectiveness review found that the reported cost-effectiveness of chiropractic manipulation in the United Kingdom compared favorably with other treatments for back pain, but that reports were based on data from clinical trials without sham controls and that the specific cost-effectiveness of the treatment (as opposed to non-specific effects) remains uncertain.[131] A 2005 systematic review of economic evaluations of conservative treatments for low back pain found that significant quality problems in available studies meant that definite conclusions could not be drawn about the most cost-effective intervention.[132] The cost-effectiveness of maintenance chiropractic care is unknown.[16]
Some chiropractors oppose vaccination and water fluoridation, which are common public health practices. Chiropractors' attempts to establish a positive reputation for their public health role are also compromised by their reputation for recommending repetitive life-long chiropractic treatment.[22] Within the chiropractic community there are significant disagreements about vaccination,[12][67] one of the most cost-effective public health interventions available.[133] Most chiropractic writings on vaccination focus on its negative aspects,[12] claiming that it is hazardous, ineffective, and unnecessary. Some chiropractors have embraced vaccination, but a significant portion of the profession rejects it, as original chiropractic philosophy traces diseases to causes in the spine and states that vaccines interfere with healing. The American Chiropractic Association and the International Chiropractors Association support individual exemptions to compulsory vaccination laws, and a 1995 survey of U.S. chiropractors found that about a third believed there was no scientific proof that immunization prevents disease.[67] The Canadian Chiropractic Association supports vaccination;[12] a survey in Alberta in 2002 found that 25% of chiropractors advised patients for, and 27% against, vaccinating themselves or their children.[134]
Early opposition to water fluoridation included chiropractors, some of whom continue to oppose it as being incompatible with chiropractic philosophy and an infringement of personal freedom. Recently, other chiropractors have actively promoted fluoridation, and several chiropractic organizations have endorsed scientific principles of public health.[135]