Placebo and Nocebo Effects in Pain: How Words and Context Shape Recovery

What if we could affect someone’s treatment outcomes without a pill, injection, or procedure—but by uttering a sentence? What if the biggest risk in the gym isn’t a rounded back during a deadlift or the knees caving in during a squat but a socially transmitted fear of such movements? Every word a clinician chooses, every explanation given by a trainer, and every expectation set by friends, family members, or society can quietly amplify real sensations of pain relief or contribute to disability, chronic pain, and fear avoidance. While many healthcare providers recognize the importance of a biopsychosocial perspective, they may not fully appreciate how often their treatments work through psychological and social pathways, sometimes as much as—or more than—the biological mechanism being targeted.

Painful conditions like chronic low back pain and arthritis are among the most common reasons for visiting a physician.¹  Despite being so common, pain is still poorly understood among healthcare providers and the patients suffering with these conditions. 

The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage,” ² The IASP describes how pain is always subjective and complex in that it can be influenced by input from our muscles, joints, and other tissues, but also from learned experiences throughout life, our emotions, and many social and environmental factors.

What does this mean for people experiencing pain and for health care providers treating them? It means that the pain and disability people experience go beyond what’s happening in the physical tissues alone. Stress, fear, anxiety, depression, and social contexts can have negative impacts on our experience of pain, while optimism, confidence, and reassurance can impact it positively.

Knowingly or not, health care providers influence these psychological and social factors on pain through their interactions with patients, by providing treatments to manage pain, and by educating patients on their condition, its prognosis, and proposed management strategies. Even when a treatment is performed with a physiological or anatomical clinical basis, there are effects at the psychological and social levels. 

When most folks seek treatments for the subjective experience of pain, they often expect and are prescribed interventions that target the presumed anatomy or physiology of the pain. Treatments like injections, massage, chiropractic adjustments, dry needling, acupuncture, and even surgery are applied for their proposed anatomical and physiological effects but have varying effects on these psychological aspects of pain, even when apparently focused directly on the painful area. 

The ability of these treatments to have a positive effect on a subjective experience like pain may be in part, or entirely, due to placebo effects. In contrast, nocebo effects can have opposite, negative effects and worsen a patient’s experience. 

This article will explore placebo and nocebo effects, popular theories as to how they work and their role in a variety of treatments and discussions around pain. It will also give practical applications as to when placebo treatments may be okay to use and how clinicians might use placebo effects to their advantage.

What Are Placebo and Nocebo Effects?

The word placebo comes from the Latin word ‘placere’ which means ‘to please.’ The opposite of placebo is nocebo. The word nocebo comes from the Latin word ‘nocere’ which means ‘to harm.’

Early use of the word placebo in medical contexts dates back to the 18th century and referred to prescribing inert drugs or inactive substances for satisfaction of the patient’s perceived need for a remedy.³ These placebos were used more to please the patient than to treat the underlying physiology.

Fast forward to 1955 when Dr. Henry Beecher, an early researcher on placebo effects in medicine, published a now famous paper stating that there were not only real but robust effects from placebo or “dummy” treatments for a wide array of conditions from wounds to headaches to angina.⁴ 

In medical research, placebos are used to discern whether or not the effects of a medicine or intervention is due to the physiological effects of the medicine, or from other factors attributed to placebo effects. Typically a placebo is a “sham” intervention, delivered as either a harmless pill, an inert medicine, or sometimes even a “pretend” medical procedure. For example, researchers investigating whether or not a medication significantly lowers blood pressure may give one group the medication and the other group an inert pill that was the same size and color and taken at the same frequency. This would allow both groups to have the same psychological or social effects of the treatment, but only one group would experience the true physiological effects since only one group received the real medication of interest. 

This type of research, a “double-blind, randomized, placebo-controlled trial”, is considered very high quality when designed and performed appropriately. These studies can also be applied to physical interventions using “sham” procedures.

While these studies can inform us of the effectiveness of a medicine or intervention, it often provides us with another interesting finding: people in placebo groups often experienced some benefit or the same amount of benefit as the real intervention group. 

Are Placebo Effects Real?

The Knee Surgery Study (2017): A landmark study of 144 patients with meniscus tears found no significant difference in pain or function between those who received a real meniscus repair surgery and those who received a “sham” placebo surgery at a 2-year follow-up. This study took 144 patients with knee pain and non-traumatic tears of their knee meniscus into two groups: 70 to receive an arthroscopic scope plus surgical repair and 74 to receive just the arthroscopic scope and a “placebo-surgery.” The patients were blinded to which group they were in. Those in the placebo group got knocked out (medically, of course), woke up with a scar, and were told they received the treatment. The other group experienced the same procedure but actually had the repair performed. Both groups experienced improvements in all outcomes measured for knee pain and function.⁵

Fortunately, patients don’t have to be knocked out and cut open to receive placebo effects from treatment.

Saline Injections for Back Pain (2024): This study told chronic low back pain patients they were receiving a placebo injection and they still experienced improvements. This is known as an open-label placebo. 101 patients with chronic lower back pain received saline injections and were told that it was a placebo treatment, not an active medication. In this study, the patients experienced significant reductions in pain and mood at 1 month follow up. This counters the idea that placebo effects need to be “snuck in” by the clinician to boost patient outcomes and that patients can knowingly receive a placebo and still experience improvement.²⁰

These very real placebo effects seem to be most significant in patients whose conditions are defined by subjective measures – like pain, mood, or feelings of general well-being. We do not expect placebo effects to significantly lower someone’s blood lipid or Hemoglobin A1C levels, but we seem to be able to rely on a reduction in symptoms from arthritis, chronic lower back pain, headaches, and other conditions where the symptoms are measured subjectively. 

Placebo effects are very real and can cause patients to pursue ineffective treatments for long periods of time due to perceived benefit or cause clinicians to believe they are delivering effective treatments. While the ethics here are questionable, at least the patient’s experience is seemingly positive.

Nocebo effects, on the other hand, can also be significant and cause long lasting pain, discomfort, and reduced quality of life. Nocebo effects are learned either through personal experiences or observations and can occur as a result of the conversations with healthcare providers, personal trainers, friends & family, or influenced by society as a whole.

To illustrate the real effects of nocebic language on behavior and pain, let’s take a trip to a less-than-reputable mechanic.

You bring your car to a mechanic and he says that “your brakes are shot, I haven’t seen brakes this bad in years, and these look like the brakes of an 80-year-old car!” You would probably leave the mechanic and drive home exceptionally scared and fearful that your car couldn’t do what it’s supposed to do. You might drive extremely slow, take turns with caution, and grit your teeth every time you hit the brakes all because of what the mechanic told you. You may stop driving the car altogether!

Imagine this in the context of healthcare. You visit a physician for lower back pain and X-rays are obtained. The provider says “this is the worst X-ray I’ve ever seen! Your back is shot! You have the spine of an 80-year-old!” You might leave this visit being very fearful that your back could not do what it’s supposed to do, you may be scared to move, bend, and lift. These fears could then cause you to experience pain, stiffness, and loss of function whether or not the biology is contributing to your symptoms. 

These negative effects can occur because of negative expectancies due to verbal suggestions, prior learning-based experiences, social observation, mass psychogenic modeling, negatively perceived patient-clinician communications, and clinical encounters.^7,8 

Placebo effects are typically short-lived and transient. Unfortunately, however, research suggests that nocebo effects can be stronger than placebo effects and longer lasting.⁹

So, how can something as simple as an expectation of a result, a conversation with a healthcare provider, or something we saw on social media cause real symptoms in our bodies or real pain relief?

How Do Placebo and Nocebo Effects Work?

The exact underlying neurological and psychological mechanisms behind placebo and nocebo effects are not well understood — but there are a few leading theories explaining how they occur. The neurological basis for these effects is often explained through three primary models:

1. Classical Conditioning: The brain learns to associate a stimulus (like a white coat or a “back crack”) with relief based on past experiences.
2. Response Expectancy: The magnitude of relief is directly proportional to how much the patient believes the treatment will work.
3. The Bayesian Brain & Predictive Coding: The brain is a “prediction machine.” In chronic pain, the brain over-predicts pain even with light stimulus.

Classical Conditioning

Most of us are aware of classical conditioning and its accidental discovery. The Russian physiologist Ivan Pavlov was researching canine digestion when he accidentally discovered a phenomenon now known as classical conditioning – a type of learning. Pavlov’s experiment involved feeding dogs over a long period of time. In the beginning of the experiment the dogs would salivate in preparation for digestion when they would first see the food. But as time went on, the dogs began to salivate not from seeing the food but from hearing sounds associated with the food being prepared. 

Pavlov then decided to conduct a new experiment involving a bell. He rang a bell before giving food to the dogs. In the beginning of the experiment, they did not salivate at the sound of the bell. Over time as the dogs associated the ringing of the bell with the delivery of food, they learned that “bell ringing” means “food is coming.” The dogs began to salivate simply at the sound of the bell. 

This became known as a Pavlovian response or Pavlovian conditioning – now known as classical conditioning. Classical conditioning, also known as associative learning, is an unconscious process where an automatic, conditioned response becomes associated with a specific stimulus.¹⁰

How does this apply to the experience of pain or pain relief? Learned responses, whether from direct experience or what you expect the response to be can trigger a response. A patient’s past experience with a given treatment can color their future response because they are used to that response after said treatment. In other words, because this happened once (or many times) before, it will happen again.¹¹

Maybe in this case it isn’t a bell but the sound and feeling of your back cracking from a chiropractic adjustment triggering pain relief due to past experiences or social media showing sighs of relief after a back crack. Maybe it’s the act of bending forward at your spine triggering pain because a doctor told you that bending your back is bad for the discs. 

Some coincidences of timing may enhance the conditioning that occurs with pain treatments. Most pain syndromes have a natural progression, followed by “regression” back to the average or baseline. If a patient seeks out treatment when their pain is at its worst, it is likely to return back to the average level of pain regardless of receiving a treatment. If a patient receives a treatment at their worst pain level and then experiences this spontaneous regression, they would likely attribute the pain relief to the treatment, and not just the normal course of time. This learned experience of pain relief following this treatment could add to future placebo effects much like Pavlov’s dogs learned that food came after a bell.¹⁹

Classical conditioning and associative learning ties into another proposed mechanism of placebo and nocebo effects – response expectancy. 

Expectancy 

If a patient believes a treatment is going to help them, it likely will have an impact on subjective outcomes like pain or self-reported function. If a person has been conditioned to believe that bending over to the floor with a rounded back or doing a deadlift will cause pain and disability, then it could impact their experience negatively with these movements. Expectations are another mechanism by which placebo and nocebo effects can take place. 

According to the response expectancy theory, the expectations of a certain outcome, like pain reduction following a treatment or pain increases following a movement, can affect our actual experience and response.¹² An individual’s expected magnitude of effect, positive beliefs, or negative beliefs can affect this response. 

How does this play out in real life? Let’s say a patient goes into a physical therapy or chiropractic clinic with a condition like lower back pain. If they expect to experience significant pain relief from their visit and have very positive beliefs about the pain relieving treatment they are about to receive, then the magnitude of their placebo effects may be larger.

If they go to this same clinic and are told that rounding their back is bad, their hips are off level, and their spine is out of alignment – they may leave with very negative views about their body and its ability to move without pain thus causing more pain and stiffness.

So, where do these expectations come from? 

Expectations of an outcome from a treatment, movement, or exercise type can arise from various places like friends and family members, health care providers, and society as a whole. People telling you “it worked for me” and social media posts highlighting patient success stories can color our expectations positively.¹³ A friend telling you a story about how they hurt their back during a deadlift and a social media post telling you how rounding your back will cause a disc herniation can make you expect a negative outcome from deadlifts.

Social learning – watching or observing someone else having a negative experience – can have a strong nocebo effect.⁸ A post on social media for example that demonizes certain forms of movement due to their injury risk could have this effect. These results were if the learning took place in a face-to-face interaction. 

Expectations of outcomes don’t seem to affect all people equally, however. Research suggests that expectancy can be lower in people with a generally less optimistic outlook on their condition and life and in people with higher levels of anxiety.¹² Despite being told a treatment will work or seeing social media posts about a wonderful new treatment may not cause as large of a placebo effect in these populations. This seems to track since these individual’s expectations would be quite low if they have a more pessimistic view of their condition and capacity for healing.

Expectancy and classical conditioning seem to generate larger placebo effects in people with acute pain. Chronic pain, however, can be more complex. People with chronic pain often have central sensitization – an amplification of pain signals by the nervous system. A theoretical model of how placebo effects are mediated in people with chronic pain involves more than just expectancy and classical conditioning.¹⁴

Predictive Coding & Bayesian Brain

Research on how placebo mediated treatments may work in people with chronic pain postulate that the brain is a predictive machine. Our brains are constantly drawing on inputs from the body to make predictions about the experience that is to come. These inputs come from real-time sensory feedback as well as prior experiences – so the brain uses a combination of learned experiences with live stimulus to predict what the response will be. 

In people with chronic pain, the prediction to all kinds of sensory inputs is usually the experience of pain. In people suffering with chronic pain even mild physical stimuli from light touch or very light physical activity can trigger a painful response. Over time, these pain predictions can become too strong and are way out of proportion to the incoming stimulus – thanks to central sensitization, or the amplification of normal pain signals. 

Various physical treatments for chronic pain can disrupt this prediction model by giving the brain inputs that, for lack of a better phrase, don’t “make sense” to it, or violate expectations in a way that leads to new learning. This messes with the brain’s ability to predict a response, which is typically a painful response in these populations. 

Treatments that don’t have a physiological mechanism of action – but more a neuro-psychological mechanism can potentially benefit these patients by modifying the amplified experience of pain.¹⁴ In other words, these treatments are not working on the underlying physiology or anatomy but more so the brain and its ability to predict pain. In other words – these treatments use placebo effects to provide pain relief. 

While the underlying causes of placebo and nocebo effects are still in the theory and discovery stage, it is understood that it is likely a combination of classical conditioning, expectancy, predictive coding, and Bayesian Brain at play at various degrees for different people. 

All treatments that aim to improve a subjectively measured symptom such as pain, feelings of well-being, or mood work either in part or entirely via these placebo effects. Whether that treatment is in the form of a pain-relieving medication, a surgery, an injection, acupuncture, massage, or a chiropractic adjustment. 

Interestingly, these treatments can carry a longer lasting nocebo effect based on the narrative surrounding them. For example, a chiropractic adjustment may cause short term placebo effects but the notion that your spine is out of alignment and you need a specialized provider with specialized training to put it back can cause long lasting fear, stress, pain, or stiffness. 

The magnitude of these placebo and nocebo effects are not the same for all treatments in all situations. While these effects are certainly real, the size of the effect can vary significantly based on a number of individual and environmental factors.

When is a placebo more than just psychology?

While many of the proposed mechanisms of action involve our neurology and psychology it seems that the physiology gets involved as well. 

We have several mechanisms at play that affect our experience of pain and endogenous pain modulation pathways that naturally decrease symptoms, increase feelings of well-being, and lift our mood. The table below illustrates how placebo and nocebo effects can change our underlying physiology and offer insight into how these learned experiences and conversations affect our actual experience.²¹

Factors Influencing the Size of Placebo and Nocebo Effects

The size of placebo and nocebo effects varies based on several factors. There are 3 groups of factors that can influence the size of effect: factors related to the intervention, factors related to the person, factors related to the relationship of the provider and the person receiving the intervention.^{15, 21} 

Let’s explore how each of these factors could contribute to the size of the effect.

Factors Relating to the Intervention

Cost of treatment

The sunk cost bias or fallacy is an error in decision making based upon prior spending of money or time. The amount of money, time, or effort invested in a treatment can color our expectations of an outcome. Some research has suggested that when patients are told a placebo treatment costs more, the degree of the effect is larger.¹⁶

The amount of money, effort, or time spent might increase a person’s expectation of a positive outcome. A treatment that is priced more or branded as premium or exclusive might enhance placebo effects, as the patient’s expectations of relief are higher due to their perceived value of the investment.¹⁷

This may come from our desire to not feel the loss of money or time. We want the decisions we make to be good ones and the money we spend to be well-spent. This sunk cost fallacy could also cause patients to continue with an ineffective treatment because they have already invested time and money into it in lieu of trying something else. This could, in time, add to placebo effects because the patient desperately wants it to work because of the time and money spent. 

Intensity of treatment

More in depth treatments also seem to produce larger placebo effects. Treatments that are perceived as taking more skill and taking more time with the provider are perceived to be more effective and can contribute to greater placebo effects.^{17, 21} 

Surgery, for example, is possibly the most extreme intervention a person could get for pain and it carries some of the largest placebo effects. A systematic review of 17 studies including 535 patients that received “sham surgery” for chronic lower back pain experienced pain relief and functional improvement. The researchers found that over half of the patients experience clinically meaningful improvement with placebo surgical procedures.¹⁷

Providers often create theatrics around their treatments for pain in various ways, knowingly or unknowingly. Passive therapy machines making sounds and emitting lights are ways to make the procedure seem more complex. Specialized body postures, tools, language, or sounds when performing the procedure all make it seem more complex than it may be, thus contributing to larger placebo effects.

Factors Relating to the Person

Severity of the condition 

There are two competing theories as to how the severity of a condition can contribute to the size of placebo effects. 

One school of thought purports that conditions with more severe subjective symptoms, like pain, can experience larger placebo effects. The idea here is that there is more room for improvement. A patient giving a subjective pain rating of 9/10 has a lot of room to experience pain relief versus a patient with 2/10 pain. 

Conflicting research supports that shorter durations of pain with lower intensity levels could experience larger placebo effects because there has been less time and opportunity for central sensitization to occur. 

Personal beliefs

Someone’s personal beliefs or expectations can influence how much pain relief they get from a treatment. If someone expects and believes something will work, placebo effects will be larger. As noted above, expectancy can influence the size of the effect either for positive results or negative results following a treatment. 

Personality Type 

A pessimistic or optimistic view of one’s condition can color their expectations of a given treatment or movement as it pertains to pain and disability. Those with a more positive outlook on life and on their condition to improve may be more likely to experience larger placebo effects. Those with a more negative outlook on life and that hold a belief their condition cannot improve may not benefit from placebo effects and, if expected to, could get worse from treatments or movement due to nocebo effects.¹²

Factors relating to the patient-provider relationship

Patient-provider relationship

The doctor-patient relationship is an important one built on trust, mutual respect, patience, and understanding. As a patient moves through a clinical encounter with a healthcare provider there are many opportunities for relationship building.

Throughout the history taking, performance of special tests, and delivery of a report of findings the provider is building trust with the patient and setting expectations. An empathetic doctor that creates a welcoming environment where a patient feels heard and understood can lay the groundwork for a larger placebo effect through expectancy.^{15, 21}

The stronger the relationship the larger the effect for both placebo and nocebo effects. Health care providers can take advantage of this placebo effect to add on to the effects of clinically meaningful treatments by being empathetic, building trust, and developing good relationships with their patients. This relationship does not have to be with a healthcare provider to be meaningful. The same type of relationship can be established between personal trainers or coaches. 

Placebo effects are real and many factors can influence its magnitude. So, where do they fit into clinical practice?

All Treatments for Pain Are Mediated by Placebo Effects

All treatments for pain, even those that have known physiological effects, also have at least some portion of their results attributed to placebo effects. Some treatments with no known physiological benefit cause pain relief entirely from placebo effects.

If all of these treatments are producing benefits via neuro-psychological mechanisms and not entirely physiological causes, should we be doing them or advising patients to pursue them?

This question does not have a simple answer. Any healthcare intervention, including those for pain management, should weigh the risks and costs against the benefits.

If a treatment has known benefits attributable to physiological adaptations or changes in the body, then any placebo effect from the treatment could be thought of as a “cherry on top” of a useful intervention. 

If a treatment has no known benefits beyond the placebo effect, then the following checklist may be helpful to decide whether or not it is worth pursuing:

• The financial cost, time investment, and effort put into the treatment is within reason for the individual 
• The treatment is without adverse effects 
• The treatment is not displacing more effective interventions with known physiological benefits 
• The patient is properly informed as to the true effects of the treatment 

If the financial cost and time investment to the individual is small and within their means, if there are very low risks or adverse effects, and if it isn’t displacing other treatment strategies that would be more beneficial, it could be fine to pursue the treatment even if the results are entirely due to placebo effects so long as the patient understands this. 

If these placebo effects allow a patient to have lower pain and less perceived disability, and this enables them to participate in an exercise program or other health-promoting behaviors that facilitate pain reduction and improvement in function, then it could be viewed as beneficial.

Using the same framework we can decide when one of these treatments may not be a good choice. 

If a treatment carries a significant financial cost and time burden, if there are significant or common adverse effects or risks, if it is taking the place of other more impactful interventions, and if the treatment comes with a narrative not supported by evidence then it should be avoided as it may cause more harm than good. 

For example, if a patient with lower back pain pursued months of spinal manipulation treatments that came with an out-of-pocket expense instead of using a progressive exercise plan — that would be against most recommendations for back pain management. To go one step further, if this intervention was packaged with harmful narratives that promote frailty and the idea that the patient needs fixing, then any placebo effects may be outweighed by longer-lasting nocebo effects.

In most of the cases discussed so far, we are painting a somewhat negative picture of placebo effects. But what we now know about pain and pain management is that we can actually use some of these psychogenic mechanisms to help people with the subjective experience of pain. 

Using Placebo Effects for Good & Avoiding Nocebo Effects

People tend to have an overall negative view towards placebos and placebo effects. But what if we manipulated interventions that we know to be beneficial from a physiological standpoint and took advantage of additional placebo-type benefits? Could we gain additional benefit from these interventions?

Healthcare providers could leverage the placebo effect in very simple ways during patient care to get positive outcomes and improve subjective outcomes in their clinical population.

By establishing rapport and trust with your patients, by developing a strong patient provider relationship, by being optimistic and creating patient buy-in, and  by setting realistic and positive expectations when appropriate the placebo effect can be used for good to optimize clinical outcomes. 

The other side of the coin here is just as important. By avoiding language that is negative and not supported by evidence the nocebo effect can be avoided. By framing movement and the body in positive ways we can avoid the socially-learned kinesophobia that is so common after interactions with healthcare providers.

What to do next

Use better information to make pain less threatening

Pain is real, but it is not always a direct measure of tissue damage. Expectations, prior experiences,
clinician language, and the way a problem is explained can all influence pain, confidence, and recovery.
The goal is not to “think pain away,” but to use accurate information, progressive activity, and better
context to reduce fear and improve function.

If pain is limiting your training

A good plan should help you keep moving, adjust loading intelligently, and rebuild confidence without treating your body as fragile.

Learn About Coaching

If you are returning to exercise

Start with tolerable activity, progress gradually, and avoid fear-based explanations about posture, alignment, or “damage.”

View Training Programs

If you coach or treat people

Choose explanations that are accurate, reassuring, and action-oriented. Avoid language that frames normal movement as dangerous or the body as broken.

Pain & Rehab Articles

References

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