The Reference Pages are reviews of topics relevant to science and medicine. Each consists of a concise overview of the topic from a scientific perspective, an index of the most relevant posts here on SBM, links to some external resources we recommend, and our summaries of the most interesting and important research. These pages are a work in progress, and we are actively developing them over the summer and fall of 2013, starting with acupuncture, chiropractic, homeopathy, and vaccines & autism.

Overview of Chiropractic

Chiropractic was invented by D. D. Palmer, Sep 18, 1895 when he adjusted the spine of a deaf man and allegedly restored his hearing (a claim that is highly implausible based on what we know of anatomy). Based on this one case, Palmer decided that all disease was due to subluxation: 95% to subluxations of the spine and 5% to subluxations of other bones.

The rationale for chiropractic hinges on three postulates:

  1. Bones are out of place
  2. Bony displacements cause nerve interference
  3. Manipulating the spine replaces the bones, removing the nerve interference and allowing Innate (a vitalistic life force) to restore health.

There is no credible evidence to support any of these claims.

Real subluxations (partial dislocations) show up on x-ray. Chiropractic “subluxations” don’t. In view of the negative x-ray evidence, chiropractic was forced to change its definition of a subluxation from “a bone out of place” to “a complex of functional and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system and general health.”

Chiropractors are divided into straights and mixers. The straights limit themselves to chiropractic adjustments; the mixers add a variety of other methods ranging from massage to outright quackery like applied kinesiology. Upper cervical chiropractors focus on the atlas, the top cervical vertebra.

In over a century, chiropractic research has produced no evidence to support the postulates of chiropractic theory and little evidence that chiropractic treatments provide objective benefits. Research on spinal manipulation is inherently difficult, because double blind studies are impossible and even single blind studies are problematic; a placebo response is hard to rule out.

There is good evidence that spinal manipulation therapy (SMT) is effective for some patients with low back pain but that it is not superior to other treatments. There is controversial evidence of lesser quality supporting the use of manipulation for neck pain and headaches. SMT is not exclusive to chiropractic: it is also used by physical therapists, doctors of osteopathy, and others. There is no acceptable evidence that chiropractic can improve the many other health problems it claims to benefit, from colic to asthma. There is no evidence to support the practice of adjusting the spines of newborns in the delivery room or providing repeated lifelong adjustments to maintain health or prevent disease.

Up to half of patients report short-term adverse effects from manipulation, such as increased local or radiating pain; and there is a rare but devastating complication of neck manipulation: it can injure the vertebrobasilar arteries and cause stroke, paralysis, and death. Some chiropractors do not accept the germ theory of disease and only about half of them support immunization. Many of them discourage proven treatments with drugs and surgery and many want to take on the role of primary health care provider.

In their book Trick or Treatment, Simon Singh and Edzard Ernst reviewed the evidence for chiropractic and concluded: “Chiropractors… might compete with physiotherapists in terms of treating some back problems, but all their other claims are beyond belief and can carry a range of significant risks.”

Index of SBM Posts about Chiropractic

Outside Resources about Chiropractic

  • NCAMM’s summary of chiropractic is a prominent example of poor quality information about chiropractic. NCCAM is a well-funded institution with a CAM-friendly agenda, so it’s quite noteworthy that they offer such weak support for chiropractic treatment, confirming that most of the evidence is negative, inconclusive, or only weakly positive — despite being generally uncritical of the profession.
  • Wikipedia has a lengthy and well-written page specifically devoted to Chiropractic controversy and criticism.
  • was one of the first substantial chiropractic skepticism resources available on the Internet, and it remains the largest (although perhaps SBM is catching up now). Operated by Stephen Barrett, MD, and SBM’s regular guest author and chiropractic insider, Samuel Homola, DC. Most articles remain relevant despite their age.

    It’s hard to choose, but one of the most interesting pages Dr. Barrett has produced is “Undercover Investigations of Chiropractors.” In a series of informal but devious and persuasive tests, physician Stephen Barrett contrived to challenge the diagnostic skills of a number of chiropractors. The results were inconsistent, and make for some of the most fascinating and disturbing reading available about the chiropractic profession.

  • The National Council Against Health Fraud is another project of the prolific Dr. Barrett. See the NCAHF Position Paper on Chiropractic and the NCAHF Fact Sheet on Chiropractic.
  • assistant editor Paul Ingraham wrote a popular article about chiropractic controversies which provoked a significant legal incident for him (which in turn resulted in meeting Dr. Steve Novella and joining the team). He has also written a very detailed review of spinal manipulative therapy.
  • The chiropractic page on lists cases of alleged harm from chiropractic treatment, with many links to more information.
  • The Chiropractic Stroke Awareness group and are both devoted to raising awareness about the risk of stroke and death from manipulation of the cervical spine, and offer resources for people who believe they have been injured by neck manipulation. Neck911’s Statement of Concern from Canadian Neurologists is a good topic summary. Neither website seems to be well-maintained, unfortunately, but their existence and purpose is noteworthy.
  • Chirotalk: The Skeptical Chiropractic Discussion Forum — probably the only such discussion forum online. (At this time, there do not appear to be any active, skeptical Facebook or Google groups on this topic.)
  • The Skeptics’ Guide to the Universe 5×5 Podcast covered chiropractic in three parts in 2010: episode 91, episode 92, episode 93.
  • The Skeptic’s Dictionary has a substantial chiropractic entry.
  • As important as the subject is, there are only a few books criticizing chiropractic. Chiropractic books often have poor ratings in web-based bookstores, regardless of their quality, because they attract angry ratings from large numbers of chiropractors and positive ones from relatively few sympathetic or skeptical readers. Five notable examples:
  • British science writer Simon Singh was sued in 2008 by the British Chiropractic Association for criticizing spinal adjustment for children with conditions like asthma and ear infections, calling it “bogus” and pointing out the lack of evidence. The BCA withdrew its lawsuit two years later, having suffered a public relations disaster. In 2012, the Guardian published an interesting follow-up, Why we sued Simon Singh: the British Chiropractic Association speaks, in which the BCA describes the lawsuit as “one of the darkest periods in its history; one that was ultimately to cost it financially, reputationally and politically.” Singh’s case is now the most prominent modern example of legal bullying of a science writer for commenting on controversial health care, and has had important consequences for free speech in the form an important and successful campaign to reform British libel law. Singh’s story has not been told in detail in one place, although it is summarized well by Wikipedia. Singh is the author of several well-known book, such as Fermat’s Last Theorem and The Simpsons and Their Mathematical Secrets.
  • The other famous chiropractic legal case is Wilks vs. American Medical Association (AMA), fought from 1976 to 1987. Previously, AMA rules made it officially unethical for medical doctors to associate or refer patients to chiropractors. A federal antitrust suit was brought against the American Medical Association (AMA) and 10 other institutional co-defendants by chiropractor Chester A. Wilk, DC, and four co-plaintiffs. After many years of appeals, the case ultimately concluded with a ruling against the AMA, specifically finding them guilty of prevent physicians from referring patients to chiropractors (violating Section 1, but not Section 2, of the Sherman Antitrust Act). The judge expressed faith in the AMA’s goodwill and “subjective belief that chiropractic was not in the best interests of patients,” but still judged that their “concern for scientific method in patient care could have been adequately satisfied in a manner less restrictive of competition.” The AMA nows permits medical doctors to refer patients to chiropractors. “Chiropractors crowed about their victory,” writes Dr. Harriet Hall, “but it actually did little to change ‘discriminatory’ practices or to enhance the reputation of chiropractic.”

Summary of Key Research about Chiropractic

Subluxation theory: chiropractic’s defining idea

Mirtz TA, Morgan L, Wyatt LH, Greene L. An epidemiological examination of the subluxation construct using Hill’s criteria of causation. Chiropractic & Osteopathy 2009, 17:13, 2009.

This landmark paper penned by four chiropractors is a strong indictment of a philosophical pillar of their own profession, subluxation theory. Although a bit of a moving target over the years, subluxation theory generally refers to idea that spinal joint dysfunctions have broad health significance, which has been a major component of chiropractic thought since the founding of the profession (see Homola, Subluxation Theory: A Belief System That Continues to Define the Practice of Chiropractic). Dr. Harriet Hall in The End of Chiropractic, one of the most commented-on posts from that year:

Timothy A. Mirtz, Lon Morgan, Lawrence H. Wyatt, and Leon Greene analyze the peer-reviewed chiropractic literature in the light of Hill’s criteria, the most commonly used model for evaluating whether a suspected cause is a real cause. They ask whether the evidence shows that chiropractic subluxations cause interference with the nervous system and whether they cause disease. The evidence fails to fulfill even a single one of Hill’s nine criteria of causation.

Mirtz et al. conclude (emphasis added):

There is a significant lack of evidence in the literature to fulfill Hill’s criteria of causation as regards chiropractic subluxation. No supportive evidence is found for the chiropractic subluxation being associated with any disease process or of creating suboptimal health conditions requiring intervention. Regardless of popular appeal this leaves the subluxation construct in the realm of unsupported speculation. This lack of supportive evidence suggests the subluxation construct has no valid clinical applicability.

Vertebral subluxation

Cassidy JD, Boyle E, Côté P, He Y, Hogg-Johnson S, Silver FL, Bondy SJ. Risk of Vertebrobasilar Stroke and Chiropractic Care: Results of a Population-Based Case-Control and Case-Crossover Study. Spine (Phila Pa 1976). 2008 Feb 15;33(4 Suppl):S176-83.

Since its publication, “the Cassidy paper” has been the defensive citation used by chiropractors to respond to accusations that neck adjustments involve a risk of stroke, and therefore should not be conducted without proven benefit and informed consent. The abstract seems to strongly exonerate chiropractors: “We found no evidence of excess risk of VBA stroke associated chiropractic care compared to primary care.”

“But abstracts are like movie trailers,” as Dr. Mark Crislip wrote. “They give a flavor of the movie, but often leave out many important plot devices and characters. … If you were to read this article in its entirety, you would not be so sanguine about the safety of chiropractic.” He goes on to explain exactly why in one of SBM’s earliest popular posts, Chiropractic and Stroke: Evaluation of One Paper.

Spinal manipulative therapy (especially for back pain)

Rubinstein SM, Terwee CB, Assendelft WJJ, de Boer MR, van Tulder MW. Spinal manipulative therapy for acute low-back pain. Cochrane Database of Systematic Reviews 2012, Issue 9. Art. No.: CD008880.

If it were possible to report good news about spinal manipulation, it would be in this large Cochrane review of the science. Unfortunately, the good news is not here to report. Historically, spinal manipulative therapy (SMT, a.k.a. chiropractic adjustment) for acute low back pain has been regarded as the best example of evidence-based care routinely offered (primarily) by the chiropropractic profession. Even many fierce critics of chiropractic have supported this claim (or at least left it alone while focusing on other issues, e.g. the risks of cervical manipulation). Nevertheless, critics have pointed out that even this “best” use of SMT has been damned with faint praise by the research. This meta-analysis supports the most critical view: the authors concluded that “SMT is no more effective in participants with acute low-back pain” than shams and placebos. Despite this, the rest of their conclusions seem crafted to prolong the controversy. They explain to clinicians why they should still refer patients for SMT (“preferences” and “costs”); they say that more research is needed to “examine specific subgroups.” (This is based on the rather faint hope that SMT might work so well for an unknown subcategory of patients that they can pull up the average.) And they say there’s a need for “an economic evaluation,” but a treatment cannot be “cost effective” if it is not effective.

The conclusions of this review are also backed up by another major review, the “Bronfort report” on the effectiveness of mannual therapies:

Bronfort G, Haas M, Evans R, Leininger B, Triano J. Effectiveness of manual therapies: the UK evidence report. Chiropr Osteopat. 2010; 18: 3.

This review of all manual therapies focusses mainly on spinal manipulative therapy and massage therapy for low back and neck pain, with underwhelming results: both are “effective” in some circumstances but certainly not impressively so, and generally no different from other therapies that help a little but haven’t exactly put a dent in the epidemic. For instance, the authors write that SMT is effective but “similar in effect to other commonly used efficacious therapies such as usual care, exercise, or back school.” Unfortunately, “back school” is not exactly well known for curing low back pain.

Together, the Bronfort and Rubinstein reviews make it clear that spinal manipulative therapy is probably only of minor clinical value, at best.

Summaries of Mirtz, Rubinstein, Bronfot, Cassidy by SBM assistant editor Paul Ingraham, also the author of a low back pain book and a detailed review of spinal manipulative therapy.

Ernst E, Carter PH. A systematic review of systematic reviews of spinal manipulation. J R Soc Med 99:192,196, 2006.

Summary: A systematic review of systematic reviews published between 2000 and 2005, based on 16 studies that met the criteria. “Overall, the demonstrable benefit of SM seems to be minimalin the case of acute or chronic back pain; controversial inthe case of headache; or absent for all other indications… we have found no convincing evidence from systematicreviews to suggest that SM is a recommendable treatment optionfor any medical condition.”

Assendelft WJJ, Morton SC, Yu El, Suttorp MJ. Spinal manipulative therapy for low-back pain. Cochrane review 2004.

Summary: A systematic review of 39 trials found that spinal manipulation was more effective in reducing pain and improving the ability to perform everyday activities than sham therapy and therapies already known to be unhelpful. It was no more or less effective than medication for pain, physical therapy, exercises, back school, or the care given by a general practitioner.

Gross A, Hoving JL, Haines T, Goldsmith CH, Kay TM, Aker P, Bronfort G. Manipulation and mobilization for mechanical neck disorders. Cochrane Review, 2004.

Summary: A systematic review of 33 trials showed that multimodal care with mobilization and manipulation combined with exercise was superior to no treatment, that manipulation was not superior to mobilization, and that manipulation and mobilization alone were not superior to placebo, control groups and other treatments.

Gouveia LO, Castanho P, Ferreira JJ. Safety of chiropractic interventions: a systematic review. Spine 34(11) E405-13. 2009.

Summary:  A systematic review of 46 studies found that 33-60% of patients receiving spinal manipulation treatment report short-term adverse effects such as increased pain, radiation of pain, headaches, vertigo and even loss of consciousness. It acknowledged that serious complications occur but was unable to reliably estimate their incidence. This study was discussed at Adverse Effects of Chiropractic

Rothwell, DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke: A Population-based case-control study. Stroke 32:1054, 2001.

Summary: Patients with a vertebrobasilar artery stroke who were under the age of 45 were 5 times as likely as controls to have visited a chiropractor during the week preceding their stroke.

Cherkin DC, Deyo RA, Battie M, Street J, Barlow W. A comparison of physical therapy, chiropractic manipulation, and provision of an educationsl booklet for the treatment of patients with low back pain. NEJM, 339:Vol 15:1021-1029, 1998.

Summary: “For patients with low back pain, the McKenzie method of physical therapy and chiropractic manipulation had similareffects and costs, and patients receiving these treatments hadonly marginally better outcomes than those receiving the minimalintervention of an educational booklet. Whether the limited benefits of these treatments are worth the additional costs is open to question.”