How yoga teachers inadvertently use placebos and nocebos

Figure 1: Nail in boot. Oh! The pain!
Figure 1: Nail in boot. Oh! The pain!

Imagine the pain! The nail had gone into the bottom of his work boot, right through his foot and was poking out the top of the shoe (see figure 1). The tradesman was in such agony that the emergency department physician had to give him powerful pain killers before taking the 6 inch nail out. Once the boot was finally removed, they discovered that the nail had actually missed his foot and gone between the toes! He had suffered no injury at all, and yet the pain was real and intense, until the boot was removed[1]. This, my friends, is a perfect example of a nocebo, which is the opposite of a placebo.

Words matter. When a doctor, therapist, counsellor or even a yoga teacher predicts something positive will happen, even if there is no scientific evidence to support the statement, often something positive does happen. That is the placebo effect. Unfortunately, the converse is true—if a statement is made that something negative might happen, it often does. This is the nocebo effect. Think about what this means for yoga teachers. Often, with best of intentions, to avoid harm to their students teachers will predict harm could arise if specific instructions are not followed. An ethical dilemma arises: should teachers warn of possible problems when the mere warning itself can cause the problem? But, what if no warning is given and something negative happens? Which is the ethical approach?

The Placebo

Placebo is from the Latin and means, “I shall please.” Placebos can occur in two distinct ways: 1) an inert substance is given along with the suggestion that this “medicine” will speed healing, reduce pain or otherwise make you better, or; 2) nothing different is given but a positive suggestion alone suffices to stimulate well-being. An example of this second situation occurs when a patient is given the same treatment or prescription as everyone gets but with an added assurance that it will work. In most cases the additional assurance is sufficient to improve healing.[2]

How placebos work is not totally understood, but they affect us both psychologically and physiologically: they seem to work due to both expectation and conditioning[3]. Placebos can reduce anxiety, alter hormone levels and increase our body’s opioid levels, which reduce pain.[4] Placebos are effective in a wide variety of ailments and conditions: from reducing and managing pain to decreasing symptom from Parkinson’s disease; from improving depression to improving immune function.[5] In most cases it is considered ethical to induce a placebo response even though no active therapeutic agent is involved. Just the reassuring smile of the doctor as she gives you your prescription is enough to activate the placebo response. Who can question the ethics of a smile?

When a yoga teacher promises that a deep twist will help to detoxify the liver and improve health, even though there is no scientific evidence for this, and students feel better—that too is a placebo effect. Is this use of a placebo ethical? Not everyone would agree. In the medical community placebos are commonly used[6], but their use is at least based on sound reasoning. In the yoga community there is a lot of unfounded hyperbole based on some rather outlandish claims of miraculous healing.[7] If the use of a placebo is based on deliberate deception, but it still proves to be helpful, is it unethical? In one study 46% of doctors believed the clinical use of placebos were ethically acceptable.[8] Presumably then, most doctors don’t believe they are ethical, however, these doctors probably use placebos without realizing it: simply assuring their patients of a good outcome can invoke the placebo effect. Shouldn’t yoga teachers be allowed the same leeway in assuring their students of health and wholeness?

Figure 2: Image from Pharmawar.
Figure 2: Image from Pharmawar.

The Nocebo

At least everyone can agree on this: it is never ethical to deliberately use a nocebo. A nocebo is from the Latin, “I shall harm!” Unfortunately, they are often invoked unwittingly. Anytime a negative prediction is given by a clinician, therapist, doctor or even a yoga teacher, the patient, subject or student often experiences a worsening of their state, pain or condition. Examples range from the trite (“this may sting a little bit”) to the severe. In a trite situation, warning a patient that a needle may hurt a little makes the pain worse than when no warning is given. At the other extreme, a nocebo may lead directly to death, as suspected in the oft-cited and unfortunate case of Sam Londe.

Sam Londe, retired, newly remarried, and living near St. Louis, noticed that he was having trouble swallowing. His doctor discovered the cause: metastatic esophageal cancer. This was in the 1970’s when such a diagnosis was a death sentence. It was incurable, but surgery was proposed to extend the time Sam had remaining. The surgery itself went well, but unfortunately the cancer had already spread to Sam’s liver. Sam was told that he had at best just a few months to live. To help Sam’s wife take care of him they moved to her family’s city, Nashville Tennessee. There Sam was attended to by a physician named Clifton Meador. Sam’s main request of Dr. Meador was to get him through the upcoming Christmas holidays so he could enjoy the holiday season with his wife and her family. By the 2nd of January, Sam Londe passed away.

There was nothing surprising about Sam Londe’s death. Liver and esophageal cancer along with his failing health guaranteed that he would not survive. What was surprising about Sam Londe was his autopsy, which revealed a tiny amount of cancer in the liver and no esophageal cancer at all. The diagnosis of liver cancer was the result of a false positive scan. Sam died with cancer, not from cancer. Sam died because he and everyone around him believed he was going to die. Sam died of a nocebo.[9]

Expectations are the key to the success of a placebo and the harm of a nocebo. While not studied nearly as much as the placebo effect, recent nocebo studies show that negative verbal suggestions can trigger anxiety, increase pain, decrease immune function and generally supress health. This is illustrated in a TED talk by pain researcher Lorimer Moseley (see below) who had a severe reaction to a simple scratch because he believed he was bitten by a poisonous snake.



“Homo homini medicamentum est” or “The doctor is the drug!”

Attitude and beliefs have a big effect on our health. Not just our own attitude but also the beliefs of those we look up to and seek counsel from. That includes, obviously, our doctors and therapists but it can also extend to our yoga teachers. Everyone who seeks to help us gain health wishes for us to be well, but not everyone who does so is aware of the power and problems of the nocebo. An ill-advised comment can often undo all the good that the therapy promised.

For example, listing the potential side effects of a drug can often initiate those effects.[10] If the side effects were not mentioned, they may not have arisen! Even a well-intended statement can cause harm: for example—when a teacher directs her students in Triangle Pose to “engage the quadriceps to prevent hyperextension of the knee,” she is implying that a hyperextended knee is dangerous. (There is a separate discussion we can have over whether this fear is valid or not, whether there is a danger to a hyperextended joint or not, but that is not the point here.[11]) Raising a red flag that a hyperextend knee is potentially harmful could actually cause a problem! It is a nocebo statement.

We know that nocebos can heighten anxiety, which can cause a cascade of pain responses. [12] Students may start to feel sensations and then pain in the knees simply due to the anxiety that they may be doing the postures wrong. With the pain comes altered walking patterns which can lead to trauma in the tissues over time. Eventually, the fear of hyperextension can by itself create problems in the knees, hips and spine.

Certainly, not everyone will be triggered by what a yoga teacher says, but there is a significant portion of the population who are more susceptible to nocebos than others. Unfortunately, yoga teachers have no idea whether the students in front of them are highly susceptible to suggestion or not. Care should be taken when forecasting any negative outcome from a posture if, in the view of the teacher, it is not done “correctly”.

The Ethical Dilemma

It is clear that a yoga teacher has a duty to inform a student when she is doing something that is potential harmful. And the student has a right to know this information. This is a basis of informed consent and if a teacher withholds information, that would be considered unethical. However, what if the warning itself can cause harm? What is the ethical path now? There is a well-known oath, first voiced by the Greek physician Hippocrates, which proclaims that a doctor’s first duty is to “do no harm.” Prevention of injury is the first priority and takes precedence over building health. This oath gives us some guidance when considering whether it is more ethical to warn students of potential problems that could arise from doing a posture incorrectly, or to remain silent and avoid creating a nocebo effect.

The parallels between the clinical situation and a yoga class are not perfect. Informed consent in medicine developed to ensure that the patient maintains her autonomy and is part of the decision process when evaluating therapeutic options. This avoids the previous paternalism that was rampart in Western medicine. However, in yoga classes, the teacher is still the one who dictates which postures are done, how they are done and for how long they are done. There is no time spent offering the student all the relevant information on other ways to do the pose and the possible benefits or dangers of each option. This is not due to some power-tripping by the teacher (although that can certainly happen!), but rather due to pragmatic considerations: there is no way to lead a drop-in yoga class and evaluate each and every posture’s efficacy for each student, and provide a full list of options, contra-indications and benefits. It should be possible, however, to empower students so that they can always refuse to do a pose, or to do it in a way that they feel works better for them.

The majority of alignment cues demanded in a yoga class have not been verified by scientific studies, and any assumption that an “improper” alignment will be dangerous for all students is speculation. The teacher has no proof that such a non-standard alignment will be injurious to any particular student. This does not mean that anything goes: there can be alignments that do have the potential to harm a particular student—the problem is, the teacher cannot know this a-priori. Rather than make a dogmatic sweeping statement that may create a nocebo effect, the teacher would be better advised to teach the student how to investigate the actual effects of her alignment choices.

Figure 3: Does this student really need fixing?
Figure 3: Does this student really need fixing?

An example can help understand this approach: when guiding a student into a Warrior Two posture (Virabhadrasana II), instead of the teacher saying “Ensure your knee is over your ankle”, which implies this is the correct, safe and only way to do the pose, she can say, “Find the place for your knee relative to your ankle that feels secure, safe and still somewhat challenging. How does this feel?[13] If this position doesn’t feel right to you, experiment a little.” This latter approach avoids the nocebo and the paternal proclamation that the teacher knows best and involves the student in finding her own appropriate posture.

Words that Heal and Words that Harm

The medical community is just awakening to the ethical dilemmas that nocebos can raise[14]. It has not been decided whether it is better to warn a patient of all possible negative outcomes in order that full disclosure is given and patient self-autonomy is maintained, or to be silent when the chances of such side effects are very low and the mere mentioning of them may induce the side effects. Even the positive effects generated by placebos are controversial because it involves deceiving the patient. However, it is more often than not decided that the placebo benefits outweigh the slight harm of deception.

Figure 4: Offering the placebo statement, “twisting can help to detoxify the liver,” may be healthy for students, even if there is no scientific evidence to support the claim.

Yoga teachers often tout benefits from the practice that have not been verified scientifically. Unless these are offered in a deliberate attempt to defraud or coerce a student, I see little harm in this practice. To say a seated twist can help detoxify the liver does not harm the student and may trigger a healing placebo effect. However, if a negative warning is given that has no scientific veracity, then a nocebo effect can occur with no commensurate gain by the student in terms of informed disclosure. Unless the teacher is certain that this particular student will suffer harm from the way she is performing a posture, then it may be better to remain silent about the supposed risk involved.

Just as the medical community has not yet come to grips with the dilemma of nocebo statements, in the yoga community this is relatively new. I have not heard many discussions on this topic and there, no doubt, will be many opinions and thoughts worth considering. In the meantime, I invite yoga teachers to consider whether it is in their students’ best interest to hear predictions of harm when the teacher has no proof that harm will happen. I would suggest, until evidence shows otherwise, that teachers reduce or eliminate negative statements. Keep the positive predictions, even if they are merely placebo statements, but beware the nocebo!



[1] I came across this story from Paul Ingraham’s website ( He says, “This source is tough for readers to confirm. It’s widely cited, downright popular, because it’s a great anecdote, but of course that doesn’t mean much. Is it for real? It is indeed. If you are determined, you can verify the citation with a free trial membership for the story is just one item in the full text of the “Minerva” column, which is a compilation of snippets of interest. See Fisher JP, Hassan DT, O’Connor N. Minerva. BMJ. 1995 Jan 7;310(70).”

[2] See Thomas KB: General practice consultations: is there any point in being positive? Br. Med J 1987; 294:1200-2. 

[3] An expectation can be created in the minds of subjects simply by saying “some people have found this (intervention) to be helpful.” Conditioning takes a bit more effort: suppose you have been given an ongoing intervention of some sort (a pill, injection or other stimulate) that has helped, but at some point the clinician substitutes a placebo for the treatment without your knowledge and you only think you are still getting the same treatment. Despite the switch, you continue to benefit. Your positive response has been “conditioned” even though there is no real intervention, just the placebo.

[4] A more complete investigation of how placebos work can be found in Placebo and Nocebo Effect: A Mini-Review by Ivan Požgain, et al in Psychiatria Danubina, 2014; Vol. 26, No. 2, pp 100-107

[5] See When Words are Painful: Unraveling the Mechanisms of the Nocebo Effect by F Benedetti et al in Neuroscience 147 (2007) 260–271.

[6] In one study, 85% of Danish doctors admitted to using placebos at least once a year, while 48% used them over 10 times a year. See The use of placebo interventions in medical practice–a national questionnaire survey of Danish clinicians by Hróbjartsson A in Eval Health Prof. 2003 Jun;26(2):153-65.

[7] See the Hatha Yoga Pradipika, circa 1400 CE, for many of these outlandish claims. For example, it is said that padmasana will cure all disease! (HYP 46-49.)

[8] See The use of placebo interventions in medical practice–a national questionnaire survey of Danish clinicians by Hróbjartsson A in Eval Health Prof. 2003 Jun;26(2):153-65.

[9] C. K. Meador, “Hex Death: Voodoo Magic or Persuasion?” Southern Medical Journal, vol. 85, no. 3: pp. 244–247 (1992).

[10] The effect of telling participants about stomach discomfort when using aspirin lead to a 6-fold increase in study drop-out rates compared to a group that was not told about the potential side effects. See Cairns JA, Gent M, Singer J, et al.: Aspirin, sulfinpyrazone, or both in unstable angina. Results of a Canadian multicenter trial. N Engl J Med 1985; 313: 1369–75.

[11] See my book, Your Body, Your Yoga for a full discussion on why hyperextension of the knee is normal and natural and most students are not at risk of injury while standing with knees hyperextended.

[12] See When Words are Painful: Unraveling the Mechanisms of the Nocebo Effect by F Benedetti et al in Neuroscience 147 (2007) 260–271.

[13] What “challenging” means is open for debate. In my view, all tissues need some stress to regain and remain healthy. So, by “challenge” I mean a place where the knee is feeling some stress, but not so much that there is pain.

[14] See The Nocebo Effect of Informed Consent by Shlomo Cohen, in Bioethics ISSN 0269-9702 (print); 1467-8519 (online) Volume 28 Number 3 2014 pp 147–154