There are a lot of case studies demonstrating the success of chiropractic adjustments for various ailments. For many chiropractors, these anecdotal reports are the proof of the pudding. But case studies should not be mistaken for reliable evidence.
Randy Ferrance, a chiropractor and medical doctor, has stated, "The plural of anecdote is not data." (1) His meaning is that no matter how many chiropractic case studies are reported, none by themselves or cumulatively rise to the level of scientific evidence. The statement itself was prompted by the frequency with which chiropractors report tales of successful interventions, especially for non-musculoskeletal maladies, intimating that the anecdotal report is scientific. The implication is that everyone with the disease is likely to benefit from this treatment and, more broadly, everyone needs regular chiropractic care to remain healthy.
In the medical world, anecdotes reported in the literature are known as case studies, also called N-of-1 trials because they involve only one subject, usually a patient who is started on a therapeutic trial and followed to see if they improve or worsen.
Case studies occupy a fairly low position on the pyramid of evidence. (2) The kinds of studies that are higher on the pyramid have greater validity. Double-blinded randomized controlled trials (RCTs) are considered the gold standard of scientific research. When properly performed, they allow valid comparison between a treatment group and a control group. Systematic reviews gather the results of similar RCTs to determine the strength of the evidence for or against a particular intervention. At the top of the pyramid are meta-analyses, essentially systematic reviews that pool the data from relevant RCTs to perform statistical analyses.
Case studies are valuable because they bring interesting results to the scientific community and suggest avenues for further research. However, they should never be mistaken for reliable treatment methods. There is a higher likelihood of bias in case studies for several reasons, most importantly because coincidence can be mistaken for causation.A patient's illness may be improved by spinal adjustments, but a case study is not capable of determining the cause. It should not be assumed that the adjustment caused the favorable outcome. The patient may have gotten better for other reasons:
Patients may get better on their own.
There is a well-known tendency for abnormal findings —lab values and clinical signs—to return to normal on repeat testing. Statisticians call this tendency regression to the mean.
The intervention may have a placebo effect.
Expectations of the doctor and the patient can bias conclusions about the treatment's effect.
A patient may exaggerate the beneficial effect of the treatment to please the doctor. (3)
An unreported intervention may have brought about improvement.
Back in my woo-woo days as an impressionable chiropractic student, I was influenced by stories of patients who were medical failures but were cured by chiropractic. In fact, I was so brainwashed by such tales that I transferred to a "straight" (4) chiropractic school in Georgia (as described here). I often listened to a cassette tape by Reggie Gold, an outspoken advocate of the straight chiropractic point of view. On the tape, Gold told the story of a soldier who was diagnosed with brain cancer and given a terminal diagnosis. The soldier asked his doctor if he should see a chiropractor. The response: "Those chiropractors will kill you." He then asked, "What will happen if I don't go?" The doctor replied, "You'll be dead in 30 days." The upshot of the story is that the soldier received chiropractic care, was cured of the cancer, and became a chiropractor himself.
More astounding than the anecdote itself is that I believed it! Of course, there are many reasons to doubt the story's veracity. Foremost is the likelihood that Gold had embellished or even completely fabricated it. After all, no evidence was offered. There are no studies published in the Journal of Chiropractic Brain Oncology (a nonexistent publication) documenting double-blind randomized controlled trials of patients with brain tumors receiving chiropractic treatment compared to a comparison group of controls treated with a placebo (which would be unethical) or with usual cancer treatments. There was not even a published case study, which could at least have shown some objective documentation of the patient's cancer and its absence following chiropractic treatment.
There are more reasons for skepticism.
The patient could have been misdiagnosed and thus "cured" of a disease he did not have.
Perhaps Reggie Gold wanted to sell chiropractic to potential patients and to convince other chiropractors of its value, so he may have been motivated by personal gain.
The patient's cancer went into spontaneous remission.
Yet another possibility is that the story is true. However, if so, we would expect to find some consistency and predictability to the claim. If chiropractic adjustments improved brain cancer, there should be other stories of similar cures and, eventually, after years of research, the world would welcome this favorable news:
Many people believe anecdotal information and mistake it for truth. This is not always a bad thing. I might try a new shampoo or vitamin supplement because a friend told me how much he was helped by it, but the risk of trying a drastic new diet and coffee enemas for cancer based on anecdotal evidence is just not worth it. A claim for the efficacy of a treatment should not be mistaken for evidence no matter how many anecdotal reports exist. The tendency to believe stories instead of seeking evidence may be due to several reasons including:
Invocation of a higher authority. "God spoke to me in a very clear language on three different occasions during a five-month period telling me to commence this work," claimed chiro-evangelist Sid Williams.
Fiat of authority or appeal to an authority figure. Authority figures include clergy, doctors, teachers, parents, and many others, dead or alive. D.D. and B.J. Palmer, the Founder and Developer of chiropractic, are often cited as authorities.
Uncritical rationalism, e.g., "knowledge" based solely on deductive reasoning from a priori truths. "We know it works because it makes sense in terms of anatomy and physiology," or "It works because the nervous system is the master switchboard of the body." (5)
Private empiricism, as when a chiropractor says, "I know it works. I've seen it proven every day in my office for 35 years."
Coincidental correlation, post hoc, ergo propter hoc—after this, therefore because of this. This fallacy of reasoning, common among chiropractors, assumes that because one event follows another then the second was caused by the first. An axiom among researchers is that correlation is not causation; just because two events occur in succession does not necessarily mean that the first caused the second. Carrots don't cause heroin addiction, but many heroin addicts have eaten carrots.
Confirmation bias. This is the tendency to believe something because it's consistent with beliefs already held and, conversely, not to accept something as factual because it contradicts cherished beliefs.
Overgeneralization. Limited evidence is used as proof of a broader theory, for example, a single experiment involving changes in T-cells is taken as evidence that "chiropractic has a profound effect on the immune system." (6)
Abstracts of chiropractic case studies proving that subluxation correction improves various health conditions appear in my email inbox as frequently as unwanted advertisements. The journals that publish them are not indexed in widely accepted medical literature databases such as PubMed. (Some chiropractic journals are indexed in these databases.) Although they claim to be peer-reviewed, the peer reviewers themselves are subluxation-based chiropractors, so it seems that the purpose of such journals is to promote pro-subluxation ideology. They serve to reinforce the beliefs of chiropractors who uncritically embrace these scientific-appearing reports of success and, in turn, motivate chiropractors to preach the "religion of chiropractic" (7) to their patients.
Here are a few of the recent abstracts I received. Some of the fallacies about anecdotes can be found in these summaries.
"Improved Health Outcomes in a Child with Down Syndrome Undergoing Chiropractic Care to Reduce Vertebral Subluxation: A Case Report & Review of the Literature." (8) This study presented the case of a seven-week-old female with Down Syndrome who presented with lactation and sleeping issues. Chiropractic examination revealed upper cervical, thoracic and sacrum subluxations. The treatment plan consisted of Toggle-Recoil adjustments of C1, diversified adjustments of the occiput and thoracic vertebrae, and Logan Basic procedure on the sacrum. After 3 visits the patient’s feeding and sleeping issues were resolved. After 2 years and 7 months of care, the infant’s muscle tone, breathing, and immune function were enhanced. The patient’s mother reported that the care helped to increase the infant’s daily "functionality" (sic) and overall health. The article concluded, "This case demonstrates a situation in which subluxation-based chiropractic care has successfully helped a patient with Down Syndrome to stimulate normal developmental activities (such as latching and regular sleep patterns) and increased her overall health (by resolving acute symptoms including constipation and respiratory issues). Further research is required to determine the effectiveness of chiropractic care in the health care of an infant diagnosed with Down Syndrome." (The article abstract can be found here.)
"Improvement in ADHD Symptomatology Following Chiropractic in a 5-Year-Old Male: A Case Report & Review of the Literature." (9) A 5-year-old male presented to a chiropractic office for history and examination for the detection of vertebral subluxation. Thermal scanning and sEMG (neither are valid diagnostic procedures) were utilized, and it was determined that vertebral subluxations were present in conjunction with spinal tension, postural faults, and reduced range of motion in the cervical spine. The patient received 54 adjustments in the upper cervical, thoracic, lumbar, and sacral regions over six months of care. Thermography and sEMG scans were performed at the initial visit and at two re-assessments. Patient progress was also monitored subjectively as the mother noted improvements in behavior. Instrumentation revealed improvement in symmetry and pattern. "The results of this case study reveal an overall positive outcome of ADHD symptomatology following chiropractic care." (See the abstract here.)
"Resolution of Gastro-Esophageal Reflux Disorder [GERD] in an Infant Following Chiropractic Care: A Case Study." (10) A seven-month-old female was suffering with unresolved acid reflux for two months. Over-the-counter simethicone as well as pediatrician prescribed Pepcid and Zantac were ineffective at resolving the gastric reflux. The infant was unable to sleep through the night due to the pain and discomfort. The infant was managed with chiropractic care using sustained contact with fingertip pressure appropriate for the infant’s age or a hand help adjusting instrument. These adjustments were performed for a total of seven visits over seven weeks. Her signs and symptoms were markedly improved and her GERD was resolved. The child was reactive, pleasant and reported to be sleeping well. "This case study supports previous information that chiropractic management may be an option for infants suffering with GERD. More research and documentation of similar cases is suggested." (Abstract available here.)
The final abstract posted here is not a case study. Rather, it's a "controlled field study" comparing two groups of subjects, one of which received chiropractic adjustments. "Chiropractic Directed at Subluxation Reduction Improves Speed of Harvest Rate, Reduces Feed Costs and Increases Feed Efficiency in Piglets: A Controlled Field Study of Rate of Gain in 109 Piglets." (11) 109 piglets weaned on the same day were enrolled in the study. Piglets were randomly assigned into control (CON) and adjusted (ADJ) groups. On average, the ADJ group reached harvest weight 6 days sooner than the CON group. Feed costs for the adjusted group were reduced and feed efficiency was improved. In conclusion, "Studying food animals in production settings can result in robust data because we can study large groups in controlled settings. Large scale studies could also determine if chiropractic can be implemented to improve sustainable agriculture by reducing antibiotic usage, improving feed efficiency, and improving consumer perceptions." (You can read the full abstract here.)
In RCTs, it's important to treat subjects in each arm of the study as similarly as possible, aside from the variable under study. In drug trials, subjects in the control group are given a placebo pill. In studies of spinal manipulation, the controls are given sham adjustments. This is not only because the controls as well as the test subjects must be blinded, but because giving attention to research subjects may in itself affect the results. In this case, the piglets in the control group wouldn't know which arm of the study they were in whether or not they received fake adjustments. However, the act of giving piglets attention in the form of human contact may alone have been the decisive factor to the favorable outcomes. Were the animals in the control group given similar attention but without the adjustments? I don't know.
Skepticism is at the heart of good science. Remember the bumper stickers saying "Question Authority" and "Question the Answers"? These statements are quite applicable to science. Whether we're talking about chiropractic or theoretical physics, healthy skepticism is a requirement. In the words of Bertolt Brecht,
The aim of science is not to open the door to infinite wisdom, but to set a limit to infinite error. (12)
He presented at a conference I attended. The quote may have originated in an article by Kenneth Kernaghan and P. K. Kuruvilla in the journal Canadian Public Administration in 1982, according to the website Quote Investigator. However, the original statement, attributed to either political scientist Raymond Wolfinger or political economist Roger G. Noll, is "The plural of anecdote is data." See here and here. back
Level of Evidence pyramid adapted from Haneline MT: Evidence-Based Chiropractic Practice, Jones and Bartlett Publishers, 2007, p.25. back
Strauss SE et al: Evidence-Based Medicine: How to Practice and Teach EBM, 3rd ed. Elsevier Churchill Livingstone, 2005. back
The term straight refers to chiropractors who limit their treatments to adjustments of the spine for the purpose of removing interference to the flow of Innate Intelligence through the spinal nerves, thus allowing the body's vital energy to heal. (Apparently Innate Intelligence can accomplish anything except getting past a misaligned vertebra.) I have discussed this idea at length elsewhere on this blog. back
Stephenson RW. Chiropractic Textbook. Davenport IA: Palmer School of Chiropractic, 1927. Stephenson's text contains 33 indisputable tenets of chiropractic philosophy. For many decades the text was required reading for students. I was tested on it when I sat for the Washington state boards in 1981. back
Most of these reasons, and others, are listed in Joe Keating's excellent article, Faulty Logic & Non-skeptical Arguments in Chiropractic, Los Angeles College of Chiropractic, 01/25/1997. (https://www.institutechiro.com/wp-content/uploads/2011/10/FaultyLogic-in-Chiro.pdf, accessed August 31, 2022.) back
This phrase comes from Holly Folk's excellent treatise: Folk H. The Religion of Chiropractic: Populist Healing from the American Heartland. Chapel Hill: The University of North Carolina Press; 2017. back
Peter Amlinger, DC & Constance Colcombet, DC, Journal of Pediatric, Maternal & Family Health, Chiropractic, July 13, 2022, Pages 57-65. back
Chris Boman, DC & Kelsey Stolarski, DC, Journal of Pediatric, Maternal & Family Health, Chiropractic, Volume 2022, May 2, 2022, Pages 33-43. back
Scott Gill, LMT, BS, DC & Amanda Gill, LMT, BS, DC, Journal of Pediatric, Maternal & Family Health, Chiropractic, April 8, 2022, Pages 22-25. back
Andrea Arbuckle, DVM, AVCA, Wyatt Fechter, Rachel Hendricks, Tate Stewart, Hannah Whetstone, Dakota Wiseman, Annals of Vertebral Subluxation Research, Volume 2022 , June 28, Pages 79-81. back
Bertolt Brecht, Life of Galileo. back