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Placebos, Nocebos, and Chiropractic Adjustments

Samuel Homola, D.C.

Appropriate spinal manipulation provides both real and placebo benefits in the treatment of mechanical-type neck and back problems. But chiropractic adjustments based on the vertebral subluxation theory may offer a placebo effect that is outweighed by a nocebo effect.

The word placebo, which is Latin for "I shall please," I first appeared in the literature in 1785 and was eventually defined as "make-believe medicine." Physicians have long known that if a patient believes in a doctor or a remedy, the response to treatment is better -- even if the treatment is a sham. Doctors quickly learned to make an effort to cultivate the confidence of their patients in order to make treatment more effective.

The beneficial effect of faith or belief in a treatment method is now known as a "placebo effect," which can occur when treatment is pretended or as an additional benefit when the treatment is real. Of course, a placebo works primarily on the mind, making the patient believe that he or she is feeling better, even though there may be no real effect on the disease itself. But there is reason to believe that a placebo effect may offer some temporary physical benefit.

Placebo Controversy

It's well known that faith in a make-believe treatment may actually help relieve pain by stimulating the brain's production of endorphins. But according to an article in the May 24, 2001, issue of the New England Journal of Medicine, such pain relief is too small to warrant use of placebos except in clinical trials [1]. The researchers concluded that there is little evidence that placebos have any powerful clinical effects or any significant effect on objective outcomes.

Three months after that report, a study published in Science reported that Parkinson's disease patients who took an inactive placebo drug experienced a substantial increase in release of a brain chemical called dopamine, temporarily relieving their symptoms [2]. "This is not a small effect," the researchers noted. "This is a big effect." The February 7, 2002, issue of Sciencexpress also reported findings challenging the NEJM report suggesting that the placebo effect is not significant. Using positron emission tomography, scans of the brain showed that inactive medication and placebos, like opioids, influenced brain centers to produce pain relief [3].

No physician would knowingly substitute an inert placebo for a proven treatment. No one would seek out a physician who treats primarily with placebos. But like it or not, the placebo effect is a part of every treatment administered by every trusted and well-liked physician or therapist. And this is okay if the placebo effect is associated with an evidence-based treatment and the patient is not given misinformation.

Placebos and Quacks

The placebo effect opens a window of opportunity for quacks and cultists who take advantage of the effect to obtain testimonial-type support for a variety of unsubstantiated treatment methods. A true quack may offer a placebo or a make-believe treatment along with a fabricated explanation that misleads patients into depending upon a nonsensical treatment method.

An alternative healer might interpret the placebo effect as proof that his particular remedy is a truly effective treatment for disease. And when remission or natural recovery occurs, as often happens, anecdotal evidence derived from patients' testimony is offered as proof that a cure has occurred.

Many alternative medicine practitioners using methods based on nonsense capitalize on the placebo effect by using it to sell courses of treatment to suggestible persons. In some cases, a treatment that initially has a positive placebo effect can ultimately have a negative nocebo effect, leading to dependence upon the treatment. This happens most often when the remedy used to treat the disease is also used to "remove the cause of dis-ease." Probably the best example of treatment that has both placebo and nocebo effects is a chiropractic spinal adjustment based on the vertebral subluxation theory. Active medications of real value can also produce nocebo effects when a patient is fearful and has expectations of adverse effects, though benefit may outweigh risk. But when a patient receives repeated spinal adjustments to correct imaginary subluxations believed to be a cause of disease, risk outweighs benefit [4].

The Nocebo Effects of Chiropractic Spinal Adjustments

There is plenty of evidence to indicate that spinal manipulation has beneficial effects -- both real and placebo. When spinal manipulation is based upon the vertebral subluxation theory, however, as presented by some chiropractors who offer "spinal adjustments" as a treatment for organic disease, nocebo effects outweigh the placebo effects. Spinal manipulation used to relieve back pain or restore joint mobility ends when symptoms are relieved and the patient is released. But when the benefits of spinal manipulation are attributed to correction of life- threatening subluxations, fear perpetuates treatment.

Many chiropractors believe that subluxations "compromise neural integrity and may influence organ system function and general health" and that spinal adjustments to correct subluxations will restore and maintain health, as noted in a position statement signed by the presidents of all of the chiropractic colleges in North America 1996 [5]. This is a scientifically indefensible position because there is no evidence that such subluxations exist. Reviews of the literature suggest that spinal manipulation is effective in the treatment of some types of neck and back pain [6,7], but this has nothing to do with the chiropractic subluxation theory.

One prominent researcher in the field of complementary medicine has suggested that the therapeutic success of spinal manipulation is largely due to a placebo effect." [8] When manipulation is used inappropriately as an ongoing treatment for elusive chiropractic subluxations, however, the nocebo effect may be more prominent than the placebo effect. Placebo effects are especially prominent in unconventional healing because of personal attention, compassionate care, enhanced expectations, and other effects of a close patient-physician relationship. A hands-on chiropractic adjustment to remove "nerve interference" caused by a "subluxated vertebra" will have a temporarily positive influence. When self-limiting conditions are involved, this placebo effect may outweigh the effects of an evidence-based treatment method. But when there is a specific disease requiring a specific treatment, a relatively impersonal, evidence-based treatment method is ultimately more effective than a placebo. When spinal manipulation is used inappropriately as an ongoing treatment for elusive chiropractic subluxations, however, the nocebo effect will eventually become more prominent than the placebo effect. An asymptomatic and elusive chiropractic subluxation is not the same as an orthopedic subluxation that can be confirmed with both subjective and objective signs. Spinal manipulation from a medical perspective is not the same as a "chiropractic adjustment." Although some chiropractors prefer to use "joint dysfunction" or some other term rather than subluxation, there is no reason to believe that vertebral misalignment or any other dysfunction in structures of the spinal column can cause organic disease [9].

Popping as Proof

Many chiropractic patients who receive spinal adjustments to restore and maintain health become convinced that they have vertebrae out of place when they hear popping sounds during treatment. Except in rare cases when a joint is truly locked or binding, the popping sound heard when joint surfaces are forcefully separated by manipulation is meaningless. This sound is most often produced by cavitation that pulls in nitrogen gas to fill the vacuum created when the fluidic attraction between joint surfaces is broken. Chiropractic patients, and many chiropractors, interpret this sound as proof that a subluxated vertebra has been moved back into alignment. The truth is that perfectly normal spinal joints will pop when manipulation forces movement into the paraphysiologic space (beyond the normal range of passive movement). Once a joint pops, it will not pop again until the gas is absorbed and the joint surfaces settle back together, usually in about half an hour. It is essentially the same as cracking one's knuckles.

If a patient is told that the pop heard during spinal manipulation means that the cause of a problem has been corrected, this can have a very powerful placebo effect, which may relieve pain as well as convince the patient that the treatment is effective. But since the vertebrae pop each time the adjustment is repeated, the patient may become convinced that vertebrae are constantly slipping in and out of place, indicating an ever-present cause of disease in the spine. The patient may then believe that illness will occur if the imaginary spinal subluxations are not corrected by regular adjustments -- a very powerful nocebo effect.

Some chiropractors take advantage of a patient's fear of subluxations by recommending regular "preventive maintenance" spinal adjustments, which contribute more to the chiropractor's pocketbook than to the patient's health. Patients of such chiropractors become psychologically addicted to treatment they do not need. James Cyriax, a prominent English orthopedic surgeon who specializes in the use of spinal manipulation, has referred to this fear as "chiropractogenic neurosis." [10]

Patient Re-education

In my forty-three years of practice as a chiropractor, I often had a difficult time convincing patients that they did not have vertebrae out of place and did not need regular spinal adjustments. On many occasions, when one of the local chiropractors was out of town, I would receive frantic calls from some of the chiropractor's patients requesting an "emergency" adjustment. "I stumbled," the patient might say, "and I have jerked some of my vertebrae out of place. My doctor is out of town and I need my alignment corrected."

Fearful that delay in correcting subluxations in the spine might trigger development of illness, some chiropractic patients become permanent patients -- victims of the nocebo effect. When I was forced to see such patients, I was compelled to inform them that nothing was wrong with their spine and that they had been misinformed. Some of these patients were actually fearful of bending over to pick up a newspaper or turn their head while backing a car lest they disturb the alignment of their vertebrae. They were literally vertebral cripples as the result of a totally imaginary problem-products of the practice-building efforts of a few unscrupulous or misinformed chiropractors.

Appropriate Spinal Manipulation is Not Alternative Medicine

Appropriate spinal manipulation is used for a specific reason for specific mechanical-type problems; when it is indicated, there is no better alternative. Spinal manipulation based upon an unproven theory that encompasses the gamut of human ailments, however, is unproven treatment, falling in the category of alternative medicine, a haven for a variety of nonsensical treatment methods.

If the chiropractic profession fails to prove or abandon the subluxation theory and train properly limited chiropractors who specialize in the care of back pain, it may continue to seek shelter under the broad umbrella of alternative medicine,

depending upon anecdotal placebo evidence and the nocebo response to justify continued use of spinal adjustments to "restore and maintain health." Without the support of evidence-based medicine, chiropractic may remain a marginal, unproven alternative healing method, making it necessary to rely upon practitioners in the field of physical medicine to supply appropriate spinal manipulative therapy. Although many chiropractors do a good job treating neck and back pain, chiropractic treatment based on the vertebral subluxation theory may do more harm than good, with many chiropractic patients becoming victims of the nocebo effect [11].


  1. Hrobjartsson A, Gotzsche P. Is the placebo powerless? An analysis of clinical trials comparing placebo with no treatment. New England Journal of Medicine 344:1594-1602, 2001.
  2. Fuente-Fernandez R and others. Expectation and dopamine release: Mechanism of the placebo effect in Parkinson's disease. Science 293:1164-1166, 2001.
  3. Ingvar M. Scans show placebo acts on brain's pain center. Sciencexpress 10 :1126, Feb 7, 2002.
  4. Barsky A and others. Nonspecific medication side effects and the nocebo phenomenon. Journal of the American Medical Association 287:622-627, 2002.
  5. Association of Chiropractic Colleges. A position paper on chiropractic. Journal of Manipulative and Physiological Therapeutics 19:633-637, 1997.
  6. Coulter I and others. The Appropriateness of Manipulation and Mobilization of the Cervical Spine. RAND 18-43, 1996..
  7. Bigos S and others. Acute Low Back Problems in Adults. Agency for Health Care Policy and Research: AHCPR publication 95-0642, 1994.
  8. Ernst B. Does spinal manipulation have specific treatment effects? Family Practice 17:554-556, 2000.
  9. Nansel D, Szlazak M. Somatic dysfunction and the phenomenon of visceral disease simulation: A probable explanation for the apparent effectiveness of somatic therapy in patients presumed to be suffering from true visceral disease. Journal of Manipulative and Physiolical Therapeutics 18:379-397, 1995.
  10. Cyriax J. Textbook of Orthopedic Medicine. London: Cassell, 1955.
  11. Homola S. Chiropractic: Does the bad outweigh the good? Skeptical Inquirer 25(1)50-53, 2001.


Dr. Homola is a second-generation chiropractor who has dedicated himself to defining the proper limits on chiropractic and to educating consumers and professionals about the field. His 1963 book Bonesetting, Chiropractic, and Cultism supported the appropriate use of spinal manipulation but renounced chiropractic dogma. His 1999 book Inside Chiropractic: A Patient's Guide provides an incisive look at chiropractic's history, benefits, and shortcomings. Now retired after 43 years of practice, he lives in Panama City, Florida. This article was originally published in the January/February 2003 issue of The Skeptical Inquirer.

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This article was posted on December 19, 2002.