Journal of Pain and Symptom Management
Volume 35, Issue 5 , Pages 544-562, May 2008

Chiropractic: A Critical Evaluation

  • Edzard Ernst, MD, PhD, FRCP, FRCPEd

      Affiliations

    • Corresponding Author InformationAddress correspondence to: Edzard Ernst, MD, PhD, FRCP, FRCPEd Complementary Medicine, Peninsula Medical School, Universities of Exeter and Plymouth, 25 Victoria Park Road, Exeter EX2 4NT, UK.

Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth, Exeter, United Kingdom

Accepted 17 July 2007. published online 15 February 2008.

Article Outline

Abstract 

Chiropractic was defined by D.D. Palmer as “a science of healing without drugs.” About 60,000 chiropractors currently practice in North America, and, worldwide, billions are spent each year for their services. This article attempts to critically evaluate chiropractic. The specific topics include the history of chiropractic; the internal conflicts within the profession; the concepts of chiropractic, particularly those of subluxation and spinal manipulation; chiropractic practice and research; and the efficacy, safety, and cost of chiropractic. A narrative review of selected articles from the published chiropractic literature was performed. For the assessment of efficacy, safety, and cost, the evaluation relied on previously published systematic reviews. Chiropractic is rooted in mystical concepts. This led to an internal conflict within the chiropractic profession, which continues today. Currently, there are two types of chiropractors: those religiously adhering to the gospel of its founding fathers and those open to change. The core concepts of chiropractic, subluxation and spinal manipulation, are not based on sound science. Back and neck pain are the domains of chiropractic but many chiropractors treat conditions other than musculoskeletal problems. With the possible exception of back pain, chiropractic spinal manipulation has not been shown to be effective for any medical condition. Manipulation is associated with frequent mild adverse effects and with serious complications of unknown incidence. Its cost-effectiveness has not been demonstrated beyond reasonable doubt. The concepts of chiropractic are not based on solid science and its therapeutic value has not been demonstrated beyond reasonable doubt.

Key Words: Cerebrovascular accident, clinical trials, cost-effectiveness, evidence-based medicine, side effects

 

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Introduction 

Chiropractic is a popular form of health care for which many definitions can be found1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 (Table 1). “The ‘raison d'être’ of the chiropractic profession is the detection and correction of spinal subluxations.”13 In the “earliest known” publication14 on the subject, its founder (Daniel David Palmer) stated that, “chiropractic is a science of healing without drugs.”15

Table 1. Recent Definitions of Chiropractic
DateDefinition/description (quotes)Source (Ref.)
1998A system of healthcare…which is based on the belief that the nervous system is the most important determinant of a person's state of health.Segen1
1994A drugless, non-invasive manual form of outpatient treatment for musculoskeletal, functional and other chronic disorders.Oths2
1996A therapeutic system based on the premise that structure and function in the human body are closely related and, in particular, the relationship between the spinal column and the nervous system is the most important.Lott3
1998A system of healing based on the belief that health is maintained when the spinal column is in its proper position and the nervous system is not impinged.Bimonte4
1998Chiropractic…is based on the body's ability to heal itself. Central to improving the body's ability to heal itself, chiropractors assert, is the removal, or correction, of malalignments of the spine (called subluxations) through the use of spinal manipulation (called spinal adjustments).Shekelle5
1998The medical profession that specializes in manual therapy and especially spinal manipulation.Kaptchuk6
1999A health profession concerned with the diagnosis, treatment and prevention of mechanical disorders of the musculoskeletal system and the effects of these disorders on the function of the nervous system and general health. There is an emphasis on manual treatments, including spinal manipulation or adjustment.World Federation of Chiropractic7
1999A profession which specializes in the diagnosis, treatment and overall management of conditions which are due to mechanical dysfunction of the joints, particularly those of the spine, and their effects on the nervous system.British Chiropractic Association8
1999A branch of the healing arts which is concerned with human health and disease processes.American Chiropractic Association9
2000A branch of the healing arts…based on the premise that good health depends, in part, upon a normally functioning nervous system.Sportelli10
2000The chiropractic is not a technique. It is a health care profession, it has an exclusive body of information which teaches, certifies, policies, purveys and sometimes attempts to validate.Halder11
2003A form of health care that focuses on the relationship between the body's structure, primarily of the spine and function.NCCAM12

Today, some chiropractors view chiropractic as an “alternative form of healthcare,”16 but in most countries, chiropractic is seen as an adjunct to rather than a replacement of conventional medicine. Chiropractors have legal recognition in about half of the world, whereas in the other half, such recognition is lacking. In India, China, former Russia, parts of Europe, and most of South Africa,17 chiropractic is not legally recognized.

In the United States, between $2.4 and $4.0 billion is spent each year on chiropractic care.18, 19 Chiropractic is covered by Medicare, a substantial proportion of private and public insurance plans, all state-workers compensation systems, all forms of managed care, most health maintenance organizations, and private health insurance plans.20 All 50 U.S. states, Puerto Rico, the District of Columbia, and the Virgin Islands license chiropractors.3, 21 About 60,000 chiropractors currently practice in North America, a number that has tripled between 1970 and 1990.16, 22 The proportion of the population using chiropractic services has doubled in the last two decades.22 The chiropractic profession is thus growing rapidly; more than 4,000 students graduate each year from about 30 chiropractic colleges in the United States, and the total number of U.S. chiropractors is predicted to reach 100,000 by 2010.23, 24

This article critically analyzes the history, rationale, and practice of chiropractic. It asks the question: Does chiropractic generate more good than harm? It draws mainly on the published chiropractic literature, including several articles that have previously reviewed chiropractic.6, 10, 11 The scarcity of critical in-depth analyses is noted; its implications are described.

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History 

The history of chiropractic is “rooted in quasi-mystical concepts.”20 Bonesetters of various types are part of the folk medicine of most cultures,25, 26, 27 and bonesetting also formed the basis on which chiropractic developed. The birthday of chiropractic is said to be September 18, 1895. On this day, D.D. Palmer manipulated the spine of a deaf janitor by the name of Harvey Lillard, allegedly curing him of his deafness.28 Palmer's second patient, a man suffering from heart disease, was also cured.29 About one year later, Palmer opened the first school of chiropractic.29

There is evidence to suggest that D.D. Palmer had learned manipulative techniques from Andrew Taylor Still (1828–1917), the founder of osteopathy.30 He combined the skills of a bonesetter with the background of a magnetic healer and claimed that “chiropractic was not evolved from medicine or any other method, except that of magnetic.”31 He coined the term “innate intelligence” (or “innate”) for the assumed “energy” or “vital force,” which, according to the magnetic healers of that time, enables the body to heal itself. The “innate” defies quantification. “Chiropractic is based on a metaphysical epistemology that is not amenable to positivist research or experiment.”32

The “innate” is said to regulate all body functions but, in the presence of “vertebral subluxation,” it cannot function adequately. Chiropractors therefore developed spinal manipulations to correct such subluxations, which, in their view, block the flow of the “innate.”33 Chiropractic is “a system of healing based on the premise that the body requires unobstructed flow through the nervous system of…innate intelligence.”34 Anyone who did not believe in the “innate” or in “subluxations” was said to have no legitimate role in chiropractic.35

“Innate intelligence” evolved as a theological concept, the representative of Universal Intelligence (=God) within each person.36 D.D. Palmer was convinced he had discovered a natural law that pertained to human health in the most general terms. Originally, manipulation was not a technique for treating spinal or musculoskeletal problems, it was a cure for all human illness: “95% of all diseases are caused by displaced vertebrae, the remainder by luxations of other joints.”37 Early chiropractic pamphlets hardly mention back pain or neck pain, but assert that, “chiropractic could address ailments such as insanity, sexual dysfunction, measles and influenza.”38

D.D. Palmer was convinced that he had “created a science of principles that has existed as long as the vertebra.”39 Chiropractors envision man as a microcosm of the universe where “innate intelligence” determines human health as much as “universal intelligence” governs the cosmos; the discovery of the “innate intelligence” represents a discovery of the first order, “a reflection of a critical law that God used to govern natural phenomena.”34

Chiropractic as a Religion 

Early chiropractic displayed many characteristics of a religion. Both D.D. Palmer and his son, B.J. Palmer, seriously considered establishing chiropractic as a religion.34 Chiropractic “incorporated vitalistic concepts of an innate intelligence with religious concepts of universal intelligence,” which substituted for science.40 D.D. Palmer declared that he had discovered the answer to the timeworn question, “What is life?” and added that chiropractic made “this stage of existence much more efficient in its preparation for the next step—the life beyond.”39

Most early and many of today's chiropractors agree: “Men do not cure. It is that inherent power (derived from the creator) that causes wounds to heal, or a part to be repaired. The Creator…uses the chiropractor as a tool…chiropractic philosophy is truly the missing link between Religion or Power of the various religions.”41 Today, some chiropractors continue to relate the “innate” to God.42 Others, however, warn not to “dwindle or dwarf chiropractic by making a religion out of a technique.”43

External Conflict 

Initially, the success of chiropractic was considerable. By 1925, more than 80 chiropractic schools had been established in the United States. Most were “diploma mills” offering an “easy way to make money,”29 and many “were at one another's throats.”41 Chiropractors believed they had established their own form of science,44 which emphasized observation rather than experimentation, a vitalistic rather than mechanistic philosophy, and a mutually supportive rather than antagonist relationship between science and religion. The gap between conventional medicine and chiropractic thus widened “from a fissure into a canyon.”34 The rivalry was not confined to conventional medicine; “many osteopaths asserted that chiropractic was a bastardized version of osteopathy.”30

Rather than arguing over issues such as efficacy, education, or professional authority, the American Medical Association insisted that all competent health care providers must have adequate knowledge of the essential subjects such as anatomy, physiology, pathology, chemistry, and bacteriology.34 By that token, the American Medical Association claimed, chiropractors were not fit for practice.28 Some “martyrs,” including D.D. Palmer himself, went to jail for practicing medicine without a licence.6, 41

Chiropractors countered that doctors were merely defending their patch for obvious financial reasons (ironically, chiropractors today often earn more than conventional doctors30), that orthodox science was morally corrupt and lacked open-mindedness.34 They attacked the “germo-anti-toxins-vaxiradi-electro-microbio-slush death producers”44 and promised a medicine “destined to the grandest and greatest of this or any age.”31

Eventually, the escalating battle against the medical establishment was won in “the trial of the century.”6 In 1987, sections of the U.S. medical establishment were found “guilty of conspiracy against chiropractors,”45 a decision which was upheld by the U.S. Supreme Court in 1990.6 In other countries, similar legal battles were fought, usually with similar outcomes.46, 47 Only rarely did they not result in the defeat of the “establishment:” In 1990, a Japanese Ministry of Health report found that chiropractic is “not based on the knowledge of human anatomy but subjective and unscientific.”48

Internal Conflict 

These victories came at the price of “taming” and “medicalizing” chiropractic.46 In turn, this formed the basis of a conflict within the chiropractic profession—the dispute between “mixers” and “straights”—a conflict which continues to the present day.

The “straights” religiously adhere to D.D. Palmer's notions of the “innate intelligence” and view subluxation as the sole cause and manipulation as the sole cure of all human disease. They do not mix any nonchiropractic techniques into their therapeutic repertoire, dismiss physical examination (beyond searching for subluxations) and think medical diagnosis is irrelevant for chiropractic.33 The “mixers” are somewhat more open to science and conventional medicine, use treatments other than spinal manipulation, and tend to see chiropractors as back pain specialists.6, 28 Father and son Palmer warned that the “mixers” were “polluting and diluting the sacred teachings” of chiropractic.39 Many chiropractors agreed that the mixers were “bringing discredit to the chiropractic.”41

The “straights” are now in the minority but nevertheless exert an important influence. They have, for instance, recently achieved election victories within the British General Chiropractic Council.49 Today, two different chiropractic professions exist side by side—“one that wishes to preserve the non-empirical, non-positivist, vitalist foundations (the straights) and the other that wishes to be reckoned as medical physicians and wishes to utilize the techniques and mechanistic viewpoint of orthodox medicine (the mixers).”32 The International Chiropractic Association represents the “straights” and the American Chiropractic Association the “mixers.”

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Core Concepts 

The three main hypotheses of modern chiropractic have been summarized as follows:16

•There is a functional relationship between the spine and health mediated through the nervous system.

•Subluxations adversely affect health.

•Correction of subluxation by spinal manipulation improves or restores health.

“Give me a simple mind that thinks along single tracts, give me 30 days to instruct him, and that individual can go forth on the highways and byways and get more sick people well than the best, most complete, all around, unlimited medical education of any medical man who ever lived.”50 This remark by B.J. Palmer implies that naivety is required to accept the implausibility of the chiropractic concepts. The founders of chiropractic created myths and denied scientific discoveries; B.J. Palmer, for instance, rejected the existence of the sympathetic nervous system,14 and early chiropractors denied the existence of the germ theory of disease, which has important implications for public health today (see below).

The “mixers,” however, saw the insistence on the “innate” as “religious baggage.”51 Today many chiropractors are anxious to sever all links with this concept,6 fearing that it might jeopardize chiropractics' acceptance into the mainstream.52, 53, 54

Subluxation 

Some chiropractors prefer terminology such as “vertebral subluxation complex,”55 “manipulable spinal lesion,”56 “chiropractic lesion,”57 or “vertebral blockage,”58 yet most modern chiropractors accept the concept of subluxation.13 The term as used in chiropractic means something different from subluxation in regular medicine. Here, I refer to the term as used in chiropractic. For D.D. Palmer, it was “a static malalignment of a single vertebra.”6 Subluxations are believed to impinge on spinal nerves, therefore blocking the flow of the “innate intelligence” (according to “straights”) or causing disease in some other way (according to “mixers”).

Many “straights” adhere to B.J. Palmer's theory that atlas subluxations impinge on the spinal cord;40 “chiropractic gets sick people well by adjusting vertebral subluxations of atlas and axis only.”59 This “narrowed the search for specific causes of patients' maladies by narrowing the area of the search to the upper spine.”14 Until recently, such chiropractic theories were left unquestioned and untested.60 Chiropractic was (and arguably is) a matter of belief rather than evidence.

Several theories have been advanced to explain how subluxations might cause health problems,61, 62, 63 for example, through edema around intervertebral foramina64 or twisting the dura mater.65 However, none of these have been independently confirmed and the specific mechanisms involved are not known.29, 66 In fact, subluxations have never been proven to constitute a relevant entity. Critics have repeatedly pointed out that even severe nerve root compression does not cause organic disease.67, 68, 69 Regardless of such doubts, the U.S. Association of Chiropractic Colleges reached a consensus in 1996 that “chiropractic is concerned with the preservation and restoration of health and focuses particular attention on the subluxation. A subluxation is a complex of functional and/or pathological articular changes that compromise neural integrity and may influence organ systems function and general health.”70 One year later, the U.S. Foundation for Chiropractic Education and Research published a monograph stating that subluxation “embraces the holistic nature of the human body, including health, well-being, the doctor/patient relationship, and the changes in the nerve, muscle, connective tissue, and vascular tissues which are understood to accompany the kinesiologic aberrations of spinal articulations.”71 Today, 88% of U.S. chiropractors believe that subluxation contributes to over 60% of all visceral ailments and 90% think it should, therefore, not be limited to muskuloskeletal conditions.72 In other countries, for example, Canada, these percentage figures are usually lower.73

Spinal Manipulation 

Subluxations can be corrected with spinal manipulations or “adjustments,” a term preferred by some chiropractors.20 Today most chiropractors agree with D.D. Palmer that spinal manipulation has to be specific, that is, at the correct spinal segment.74 There is, however, less agreement on the optimal direction or the level of manipulation.75, 76 Chiropractors even disagree about the term spinal manipulation.77, 78 In its broadest definition, it describes the “application of a load (force) to specific body or tissues with therapeutic intent.”20

Spinal manipulation moves vertebrae beyond their physiological range of motion (chiropractors speak of “end feel” and “paraphysiological space”)13 but not far enough to destroy joint structures:6 “between the normal range of motion and the limits of its normal integrity.”13 Chiropractors believe that spinal manipulation breaks fibrous adhesions within joints, or that it “releases small tags from the joint capsule that might be entrapped within the joint,” or that it affects the mechanoreceptors of the joint, or that it modulates central nervous system excitability,21 or that it inhibits C-fiber mediated pain perception.79 None of these theories are, however, supported by sound evidence.80

Numerous forms of spinal manipulation exist but “the short-lever technique—touching the vertebrae directly at high velocity and low amplitude, i.e., by moving a small distance—with the spinal or transverse process as a fulcrum, is considered the typical chiropractic manoeuver.”6

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Chiropractic Practice 

The Profession(s) 

Many chiropractors (mixers) view themselves as primary care providers30, 81 or general practitioners with “an important role in health promotion and injury or disease prevention.”82, 83 “Integrative medicine” is often seen as “the next step in gaining access to patients.”84

Overall, estimates of the use of chiropractic services by the general population range from 3% to 18%.21 Health care professionals usually prefer other forms of complementary/alternative medicine to chiropractic.85, 86 Chiropractors predominantly treat patients with musculoskeletal problems, about 60% of whom suffer from low back pain. In the United States, 13% of all back pain sufferers consult a chiropractor.87 Another domain is neck pain, which chiropractors usually treat with upper spinal manipulation. One report indicates, however, that only 11% of all cervical manipulations are “appropriate.”88

Spinal manipulation is also practiced in other professions (e.g., osteopaths, physiotherapists, and doctors) but chiropractors deliver more than 90% of all spinal manipulations.20 Treatment is often continued for over three months, even in the absence of clinical improvement.89 Consultations last for an average of 22minutes.90 Many U.S. chiropractors use “practice building seminars” (often organized by Scientologists) to convince their patients of the value of their treatments.91 Chiropractors work mostly in single practices (67%) and have an average of 3.8 years of basic training.90 Their income frequently exceeds that of conventional primary care physicians.30

The Treatments 

In addition to spinal manipulations, “mixers” also use other modalities such as heat, cold, and electrotherapy; they also may advise on supplement usage, lifestyle, weight loss, or relaxation.20 Maintenance chiropractic care is promoted as a preventative measure for both musculoskeletal and visceral problems92 even though “such unnecessary manipulation might present a risk to patients.”93 Some chiropractors refer patients to homeopaths, iridologists, or paranormal healers.94 Many chiropractors use unproven or disproven methods themselves such as homeopathy (46%), applied kinesiology (38%),95 or traction.94 In fact, applied kinesiology is rated to be among their most reliable diagnostic methods.77

“Widespread unjustified claims which chiropractors routinely make” have become a concern even for some chiropractors.96 A comparison of practice guidelines issued by various chiropractic organizations disclosed “discrepancies in the strength of recommendations, the type of recommendations and even the evidence upon which the recommendations have been based.”32

Patients 

About 90% of chiropractic patients are self-referred,84 and payment often comes (35%) directly from the patient.90 Chiropractic patients are more likely than medical patients to be obese, lack a regular doctor, have few chronic conditions, take few drugs, and be uninsured and dissatisfied with health care.97 A sizable proportion of U.S. chiropractic patients (20%–30%) receive in excess of 11 treatments sessions.81 For neck pain, an average number of 25 visits was recently reported, and 2% of these patients received more than 80 treatment sessions.98 In other countries, for example, Canada, these percentages may be considerably lower.99

Reasons for patients not to consult chiropractors include the fear of adverse effects and “lack of scientific proof.”84 In general, the public seems to prefer medical doctors as their primary care providers.100 In some parts of Canada (British Columbia and Ontario), chiropractic services have recently been delisted, and the Ontario government estimated that $100 million will be saved through this move.101

Indications 

Chiropractic services are used mostly, but by no means exclusively, for the management of musculoskeletal conditions. The American Chiropractic Association stresses, however, that chiropractic care is “not limited to back pain, neck pain” or other neuromusculoskeletal disorders;9 11%–19% of all chiropractic patients suffer from nonmusculoskeletal conditions.102, 103 This figure seems to be considerably lower outside the United States.94, 104

Most chiropractic texts discuss spinal manipulation as a treatment for visceral disorders,13, 16, 105, 106 and it has been noted that, “there have been over 1,200 published studies linking spinal trauma to visceral disease.”107 Nonmusculoskeletal problems regularly treated by chiropractors include respiratory conditions, nonspinal injuries, digestive system disorders, menstrual problems, ear infections, pregnancy-related conditions, infectious and parasitic conditions, dermatological diseases, and acute urinary conditions.81 Chiropractors cite uncontrolled studies in support of spinal manipulations for indications such as dysmenorrhea, asthma, otitis media, hypertension, IBS, and peptic disorders.108, 109, 110, 111, 112 The chiropractic literature is rife with claims related to nonspinal indications, for example, “the judicial use of chiropractic services in cancer patients appears to offer many economical and effective strategies for reducing the pain and suffering of cancer patients….”113

Diagnostics 

The reliability of diagnostic techniques used by chiropractors is generally poor.75, 114, 115, 116, 117, 118, 119, 120, 121 Plain static radiograph and functional radiograph investigations are viewed as the most reliable methods for diagnosing subluxations.77 Thus, practically all new (96.3%) and most continuing (80%) U.S. chiropractic patients undergo radiography, with an average number of views per new patient of 3.4.102 Yet, guidelines state that a competent chiropractor “does not do routine radiographs on every patient.”122 The majority of U.S. chiropractors (86%) have their own X-ray equipment,102 whereas elsewhere, for example, in Holland, this figure is lower (58%).94 Although most patients consulting a chiropractor have a radiograph taken,123 only 4% of UK back pain patients in general practice have the procedure.124 Most experts today caution that radiographic investigations for nonspecific back pain are frequently unnecessary125 and harmful.126

Many U.S. chiropractors also do blood and urine analyses and some engage in minor surgery.81 In Oregon, chiropractors are allowed to deliver babies,127 but in most U.S. states, obstetrics is specifically prohibited to them. Conventional U.S. doctors are unlikely to make formal referrals to chiropractors.128

Ethics 

A comparison of Californian disciplinary actions (1998–2002) against chiropractors and medical doctors showed that there were 4.5 such actions per 1,000 chiropractors per year, a figure which was 98% higher than that for doctors. The incidence rate per 1,000 for fraud was 1.99 for chiropractors, 895% higher than that for doctors. The incidence rate for sexual boundary transgressions was 1.01 for chiropractors, 339% higher than that for doctors.129

Informed consent is a serious concern in chiropractic practice. Of 150 randomly selected UK chiropractors, only 23% reported always discussing serious risks with their patients before treatment, a behavior that clearly is in conflict with the UK ethical code.130

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Research 

The terms “research” and “science” appear frequently in the chiropractic literature with a variety of meanings “unfamiliar to most scientists”33 (Table 2). Many early chiropractors felt the need to obtain an “aura of scientific respectability” as marketing ploys for promoting their practice to the public.33 This attitude seems to be still prevalent. A leading Canadian chiropractor, for instance, was quoted saying that research “is something that you have to do, no question. We have to have the research to be accepted properly.”131 The concept that research is a means of improving future health care does not seem widespread within the chiropractic profession.

Table 2. Quotes from the Chiropractic Literature Related to Science
DateAuthorQuote
1897Palmer DDChiropractic is a science of healing without drugs
1906Palmer DD, Palmer BJThe science of chiropractic
1910Palmer DDThe science, art and philosophy of chiropractic
1911Palmer BJThe philosophy, science and art of chiropractic nerve tracing
1917CarvorThe first scientific statement of the science of chiropractic
1946Ratledge TFThe ultra-scientific nature of the chiropractic concept
1985DishmanScientific basis for the chiropractic subluxation complex
1994Martin SCThe demonstration of a new scientific law that healed the sick was an important contribution to the revealing of God's beneficence

The little research that did take place during the early years of chiropractic was of remarkably low quality. Research was initiated to prove rather than to test chiropractic.33 The data that thus emerged were subject to “zealous overinterpretation.”33 For instance, observational studies were wrongly characterized as controlled clinical trials.132 The current chiropractic research literature continues to be overtly biased. An evaluation of the 29 recent reviews of spinal manipulation for back pain concluded that those authored by chiropractors tended to generate positive results, whereas the others failed to demonstrate effectiveness.133

Today's “straight” chiropractors believe that research “never establishes truth”42 and deny the relevance of science to chiropractic.35 “We cannot second guess whether the innate intelligence of the body can heal a disease.”42 Belief in subluxation is an essential prerequisite for any chiropractor—so much so that questioning this belief is grounds for banishment from the profession; therefore, scientific investigation of chiropractic, which obviously requires questioning that belief, is (by definition) not possible for chiropractors.33

There is “a shortage of chiropractic clinicians who have the experience and training to conduct clinical research.”112 A survey of Californian chiropractic students suggested that 52% of them are interested in research, 26% have research experience, 19% thought research training should be in their curriculum but “most students…were reluctant to take on extra courses in research.”134 It is, therefore, not surprising that “many of the key clinical trials…were conducted in Europe and Canada.”13

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Current Evidence 

Efficacy 

Kusserow noted that, “overtly aggressive marketing [is]…deliberately aimed at misleading patients and the public regarding the efficacy of chiropractic care.”135 In fact, unsubstantiated claims regarding the efficacy of chiropractic continue to be made, not merely by overenthusiastic individuals but also by official organizations. For instance, a patient brochure published by the UK General Chiropractic Council (the body that oversees chiropractic in Great Britain) stated that “chiropractors primarily treat: spine, neck and shoulder problems, joint, posture and muscle problems, sciatica, sports injuries, tension headaches and benefit may also be seen for some types of asthma, digestive disorders, migraine, infant colic, menstrual pains.”136 This statement clearly implies that chiropractic is helpful for these indications. Yet the evidence from rigorous clinical trials fails to confirm this.

Numerous controlled clinical studies of chiropractic are now available, but their results are far from uniform. Rather than selecting single studies according to their findings, it is, therefore, preferable to consider the totality of this evidence. Table 3 gives an overview of the most up-to-date systematic reviews by indication.137, 138, 139, 140, 141, 142, 143, 144 These systematic reviews usually include trials of spinal manipulation regardless of who administered it. Thus, they are not exclusively an evaluation of chiropractic. Collectively, their results fail to demonstrate that spinal manipulation is effective. The only possible exception is back pain. For this condition, manipulation may be as effective (or ineffective) as standard therapy.137

Table 3. Systematic Reviews of (Chiropractic) Spinal Manipulation
First Author (Year)InterventionsConditionnMeta-analysisOverall resultaComment
Assendelft et al. (2004)137Any type of SMLow back pain39YesNo evidence that SM is superior to other standard treatments for acute or chronic low back painAlso included RCTs of mobilization
Gross et al. (2004)138Any type of SM and mobilizationNeck problems33Yes…evidence did not favor SM/mobilization done aloneCombined with exercise, SM was beneficial
Fernandez-de-las-Penas et al. (2006)139All types of manual therapies (3 trials of spinal manipulation)Tension type headache (TTH)6No“…no rigorous evidence that manual therapies have a positive effect on the evolution of TTH”2 RCTs were of high quality but generated contradictory results
Ernst (2003)140Chiropractic SMNeck pain4NoThe notion that chiropractic SM is more effective than conventional exercise…was not supported by rigorous trial dataIncluded only RCTs of chiropractic SM.
Proctor et al. (2001)141Any type of SMPrimary and secondary dysmenorrhea5NoThere is no evidence that SM is effective4 of the 5 RCTs were of high velocity, low amplitude thrusts
Husereau et al. (2003)142Any type of SMInfantile colic4NoNo convincing evidenceMost trials were of low methodological quality
Balon and Mior (2004)143Chiropractic careAsthma/allergy6NoNo evidence to support the use of chiropractic SM4 of the 6 trials tested SM; 3 of these studies were negative
Reid and Rivett (2005)144Manual therapy mainly manipulation and mobilizationCervicogenic dizziness9No…there is limited evidence at present to support the use of manual therapy in treating cervicogenic dizziness.Only one of the trials was randomized.

This table includes all indications for which systematic reviews are available. If for any indication more than one systematic review exists, the most recent one was chosen.

n=number of trials included, SM=spinal manipulation, RCT=randomized clinical trial.

aQuote from authors' conclusions.

Many national guidelines recommend chiropractic for acute or chronic low back pain.145, 146, 147, 148, 149 The reason may not be the convincingly demonstrated effectiveness of chiropractic care but the fact that no therapy so far has been shown to make a real difference for back pain sufferers. Recent studies suggest that a prospectively identifiable subgroup of patients with back pain may benefit from spinal manipulation, whereas others do not.150, 151, 152, 153 If this turns out to be true, it could help to explain the so far unconvincing trial results. Other recent data suggest that, for back pain, educational programs may be preferable to treatments such as spinal manipulation, which tend to medicalize back pain sufferers.154

Few of the primary studies have been adequately controlled for placebo effects, an objective which is difficult but not impossible to achieve. Thus, some of the benefit reported in the above-mentioned studies could be due to a placebo response. A survey of 34 Australian “leaders of the chiropractic profession” suggested that the majority of chiropractors agree that the placebo effect is a major contributor to the perceived benefit of chiropractic. Some even felt that “at least half” of the chiropractic success is due to placebo effects.155

According to the chiropractic literature, absolute contraindications of chiropractic include osteoporosis, local malignancies, bone fractures, bone infections, and bleeding disorders,21 as well as active inflammatory arthropathy, ligamentous laxity, hypermobility, local metastases, dislocations, myelopathy, and cauda equina syndrome.16 Relative contraindications include severe spondylosis, distant malignancies/metastases, local benign tumors, spinal trauma, chronic sponylarthropathy, history of spinal surgery, acute soft tissue or disc injuries, history of verbrobasilar insufficiency, and osteopenia.16

Safety 

Direct Risks 

“Chiropractic is safe”82—in the chiropractic literature, statements like this can be found abundantly. Table 4156, 157, 158, 159, 160, 161, 162, 163, 164 depicts some of the arguments currently used by chiropractors to deny that spinal manipulation can cause harm or to trivialize its risks.

Table 4. Quotes from the Recent Chiropractic Literature Regarding Safety
DateAuthorQuoteRef. No.
2001CohnThe occurrence of cerebral vascular accidents (CVAs) in the general population is 0.224% while the occurrence of CVAs in the chiropractic population is 0.000008%.156
2001Filippi…this latest ungrounded association [of chiropractic] with stroke etiology serves as a final straw in a long and tedious process of professional identity.157
2002Michaud…vigorous manipulation of the upper cervical spine is possible without injuring an already damaged vertebral artery.158
2003Haneline et al.The medical literature does not support a clear causal relationship between chiropractic manipulative therapy and internal carotid artery dissection.159
2003Haneline and Croft…a causal relationship [between chiropractic manipulation and internal carotid artery dissection] is not supported by the literature.160
2003Mirallas-Martinez…mortality due to surgical interventions of lumbar spine is 300 times greater than due to post-cervical manipulation stroke.161
2004Refisch and Bischoff…the relationship between cervical manipulation and lesions of the cervical arteries…must be negated.162
2004OliphantAn estimate of the risk of spinal manipulation causing a clinical worsened disk herniation or cauda equina syndrome…is calculated…to be less than 1 in 3.7 million.163
2005Haneline and TrianoThe direct evidence suggests that the healthy vertebral artery is not at risk from properly performed chiropractic manipulative procedures.164

In 2001, a systematic review of five prospective studies concluded that mild-to-moderate, transient adverse effects are experienced by about half of all chiropractic patients.165 Local or radiating pain, headache, and tiredness are the most frequent adverse effects. Since then, two further prospective studies (n=465 and 336, respectively) reported that such adverse effects occur in 61% and 30% of patients.166, 167 Therefore, there is undeniable evidence that chiropractic is associated with an exorbitantly high incidence of minor adverse effects.

Spinal manipulation of the upper spine has frequently been associated with serious vascular accidents. A systematic review summarized the data up to November 2001,168 and an update reviewed the latest evidence.169 In total, this disclosed around 700 serious complications and about 50 deaths. Five surveys have been published asking doctors to report instances where their patients have experienced serious adverse effects after spinal manipulation.170, 171, 172, 173, 174 The results invariably disclosed a multitude of complications after chiropractic manipulation. More importantly, they demonstrated that these instances had not previously been reported in the medical literature. In other words, underreporting had been 100%. Therefore, it seems highly doubtful whether reliable incidence figures can presently be calculated. A recent systematic review found 14 cases of adverse effects of spinal manipulation in children, 10 of which involved serious complications such as subarachnoidal hemorrhage or paraplegia.175 Table 5 lists a selection of recently published case reports176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191 associating chiropractic treatments with serious complications.

Table 5. Recent (2001–2006) Case Reports of Serious Adverse Events After Chiropractic Spinal Manipulation
First Author (Year)Patient(s)Adverse EventOutcome
Jeret (2001)17634-year-old man with neck pain after whiplash injuryDural tear, positional dizzinessFull recovery
Siegel and Neiders (2001)17733-year-old woman with headacheVertebral artery dissection followed by pontine infarctPermanent, severe neurological deficit
Parwar et al. (2001)17844-year-old man with shoulder painDissection of right internal carotic artery, Horner's syndromeNot reported
Schram and Vosik (2001)17947-year-old man with neck and shoulder painPhrenic nerve injury, diaphragmatic paralysis, severe dyspneaResidual dyspnea
Jeret and Bluth (2002)18031-year-old womanDissection of left vertebral arteryComplete recovery
Sedat et al. (2002)18142-year-old woman with neck painDissection of extracranial port of the right PICAResidual headache and stiffness on discharge from hospital
Jay et al. (2003)18226-year-old woman with headache and sinusitisBilateral dissection of vertebral arteries followed by bilateral occipital-parietal hemorrhagic infarction and visual impairmentNot mentioned
Menendez-Gonzalez et al. (2003)18333-year-old patientDissection of vertebral artery followed by Wallenberg's syndromeNot mentioned
Wojcik et al. (2003)18446-year-old female patient with neck painDural tearComplete recovery
Beck et al. (2003)18540-year-old female patientWallenberg syndromeNo information provided
Nadgir et al. (2003)18634-year-old manBilateral internal carotic and vertebral artery dissectionResidual left-side hemianesthesia and dysesthesia
Oehler et al. (2003)18731-year-old woman with headacheBilateral dissections of vertebral arteriesNot mentioned
Yokota et al. (2003)18838-year-old manDissection of left vertebral artery followed by Dejerine syndromeNot mentioned
Izquiedo-Casas et al. (2004)18937-year-old womanDissection of vertebral artery followed by tertraparesisFibrinolysis resulted in complete recanalization of the artery
Saxler and Barden (2004)19027-year-old womanEpidural hematoma extending from cervical to sacral spineComplete recovery
Tome et al. (2004)19140-year-old patientMultiple cervical disc herniationNot mentioned

In all cases, causality was deemed to be certain or likely, and in all instances was the therapist a chiropractor.

Indirect Risks 

Further safety concerns relate to indirect risks of chiropractic. The above-named review175 noted 20 cases of delayed or missed diagnoses through consulting a chiropractor. A similar but better researched indirect risk is the attitude of many chiropractors toward immunization. The early chiropractic literature is littered with statements against immunization. Palmer's original concepts were seen by chiropractors as a complete explanation of all medical conditions, their prevention, and treatments. Infectious diseases, therefore, put the gospel of D.D. Palmer in doubt (see above); consequently, their existence was denied, and so was the benefit of immunization. The faculty and administration of Williard Carver's “Chiropractic Research University” were even jailed for refusing “to submit to the compulsory vaccination law of the District of Columbia.”14

The current chiropractic literature continues to promote “hostile opposition to health prevention based upon immunization procedures”192 and repeatedly stresses that immunization is hazardous and ineffective.193, 194 In doing so, facts are distorted: “Smallpox vaccination was stopped in the U.S. and U.K. because it was realized that the vaccinated suffered the worst effects of the disease;”195 or the risks of immunization are exaggerated: “The dangers of vaccination to the young child are profound… in some cases, the vaccine acts non-specifically to increase a child's pre-existing chronic disease tendency.”196 Other sources state that immunization is useless and harmful: “Immunisation programmes continue on the premise of prevention” but “it cannot be said that the…programme has been proven successful…and the complication rates for the vaccines continues to claim the lives of children via disability and/or death.”197 Others again report that, “vaccination appears to increase the risk of allergies and related respiratory symptoms.”198 There is no shortage of strong statements in the chiropractic literature warning patients of “having toxic filth squirted into the bodies” of their children.192 Even though some chiropractors would probably deny this, the anti-immunization lobby of chiropractors is still very strong; the only place where chiropractors are prohibited from lobbying against immunization is in Ontario, Canada.199

A U.S. survey was aimed at identifying chiropractors' attitudes toward immunization.200 A random sample (1%) of all U.S. chiropractors was provided with a choice of policy statements. One-third of the sample agreed with the statements that there is no scientific proof that immunization prevents disease, that it causes more disease than it prevents, and that contracting an infectious disease is safer than immunization. Another survey was performed on 150 licensed chiropractors from Boston. About 30% of them reported to recommend active immunization and 7% recommended their clients against immunization.201 A Canadian interview study recently confirmed that some chiropractors provide to their patients “information of a negative, anti-vaccination nature.”202

Cost 

A World Health Organization-sponsored, systematic review of cost analyses in complementary medicine included seven investigations related to spinal manipulation or chiropractic care.203 It concluded that “there is no evidence to suggest that chiropractic is a more cost-effective treatment option than physiotherapy or hospital outpatient treatment for low back pain.”203 Since then, several new studies have become available. A UK trial compared disability scores after spinal manipulation (carried out by chiropractors, osteopaths, or physiotherapists), exercise classes, or manipulation followed by exercise in addition to care for chronic back pain by general practitioners.204 Exercise was superior to primary care at three months but not after one year. Manipulation alone or followed by exercise generated better outcomes than primary care at 3 and 12 months. Effect sizes were, however, small to moderate. The mean incremental treatment cost relative to general practitioner care was £195 for manipulation, £140 for exercise, and £125 for the combined treatment. The authors estimated the cost per Quality Adjusted Life Years as £3,800 for combined treatment and £4,800 for manipulation.

A retrospective analysis of the U.S. worker's compensation payment data from a single insurer analyzed the figures from individuals suffering from work-related low back injuries between 1999 and 2002.205 The results showed that restrictive payment policies were associated with lower cost of chiropractic care and lower number of services per visit, but did not affect the visits or services per person.

Legorreta et al.206 retrospectively analyzed claims data of more than one million members of a U.S. health care plan. Access to chiropractic care was associated with lower cost for neuromuscular complaints and back pain. This effect could be due to these patients being younger and healthier than nonchiropractic patients.207 Others have noted that users of chiropractic are also high users of conventional health services,208 which renders cost savings an unlikely prospect.

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Conclusion 

This overview will be rejected by proponents of chiropractic for being biased or one-sided, but its purpose was to offer a critical evaluation. At present, such an assessment has not been provided by chiropractors, yet progress in any field is difficult without critical evaluation.

Chiropractors' belief in the “innate,” subluxation, or spinal manipulation is not rational. Current chiropractic practice raises numerous concerns. The effectiveness, safety, and cost of spinal manipulation are uncertain. More and better quality studies are, therefore, required. Until convincing data are available, we might question the value of this popular approach to health care.

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 The author has no conflict of interest.

PII: S0885-3924(07)00783-X

doi:10.1016/j.jpainsymman.2007.07.004

Journal of Pain and Symptom Management
Volume 35, Issue 5 , Pages 544-562, May 2008

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