WHAT IS PLACEBO?

PLACEBO: THE REAL BIOLOGY AND CLINICAL SIGNIFICANCE OF A FALSE TREATMENT

Prof. Dr. F. Cankat Tulunay
www.klinikfarmakoloji.com

The concept of placebo is one of the most misunderstood, yet at the same time one of the most instructive topics in medicine. It is often defined as “a drug that contains no active substance.” However, this definition is both incomplete and misleading. The word placebo is derived from the Latin verb placere, meaning “to please.” “Placebo” means “I shall please.” Even this etymological origin shows that placebo, from the very beginning, represents the creation of expectation and meaning in the patient rather than a purely pharmacological effect.

In modern medicine, the placebo effect is not merely a psychological illusion but a real clinical phenomenon associated with measurable biological changes. The concept of the placebo effect was first systematically described by Henry K. Beecher and has become an integral part of clinical research (1). However, at the point we have reached today, it is clear that the placebo effect is not merely a “control group phenomenon” but has direct therapeutic potential.

Three fundamental mechanisms are proposed to explain the placebo effect: expectation, conditioning, and neurobiological response. Expectation is the most powerful component of the placebo effect. If a patient believes they will improve, this belief produces real changes at the level of the brain (2). Conditioning, on the other hand, is related to the generalization of previously effective treatments to new situations and represents the clinical counterpart of classical Pavlovian mechanisms (3). At the neurobiological level, it has been shown that during the placebo effect, the endogenous opioid system is activated, dopamine release increases, and networks associated with the prefrontal cortex are engaged (4–6).

When examined in more detail, the neurobiological basis of the placebo effect reveals that this process arises from the coordinated activation of multiple systems. During placebo analgesia, the endogenous opioid system is activated, and endorphin release increases, particularly via μ-opioid receptors (6). The fact that this effect can be partially blocked by naloxone demonstrates that the placebo response has a genuine neurochemical basis. In addition, studies in Parkinson’s disease have shown that placebo administration increases dopamine release in the striatum, which is associated with motor response (4). Functional imaging studies have demonstrated increased activation in the prefrontal cortex and anterior cingulate cortex related to expectation (5).

Furthermore, activation of descending pain inhibition systems via the periaqueductal gray matter and rostral ventromedial medulla indicates that the placebo effect can modulate pain transmission even at the spinal level. These findings clearly demonstrate that the placebo effect is not merely psychological but a multilayered biological organization. The variability of placebo responses among individuals suggests that this effect is also related to genetic and individual factors. In particular, polymorphisms in the COMT (catechol-O-methyltransferase) gene may modulate the placebo response by affecting dopamine metabolism (12).

In addition, individual personality traits—especially optimism, suggestibility, and trust in treatment—are important determinants of the magnitude of the placebo effect. Cultural and social context also influence this process; the meaning attributed to medications by society, trust in the healthcare system, and the authority of the physician can strengthen or weaken the placebo response. However, the critical point is this: the placebo cannot be explained by a single mechanism. It is a multilayered and heterogeneous phenomenon.

Pain is one of the areas in which the placebo effect is most strongly observed. Placebo analgesia is one of the best-studied clinical models and has been shown in many studies to produce significant pain reduction (2). In this context, migraine is one of the most striking examples of the placebo effect. In migraine studies, placebo response rates have been reported to be between 20–40%. Even more striking is that some migraine medications do not show significant superiority over placebo in the treatment of acute attacks (7).

This situation demonstrates that contextual effects in migraine treatment are extremely powerful and that pharmacological efficacy often cannot be considered independently of this context. In this respect, migraine is almost a model disease for understanding the placebo effect.

The placebo effect is not limited to pain. Studies in patients with Parkinson’s disease have shown that placebo administration increases striatal dopamine release (4). This finding demonstrates that the placebo effect can produce objective and measurable effects even on the motor system. In depression studies, placebo response rates have been reported to reach 30–40% (8), approaching the efficacy of many pharmacological treatments. A similar pattern is observed in sleep research. Particularly in patients with insomnia, the mere belief that a “sleep medication” has been taken can lead to a significant improvement in sleep quality (9).

At this point, I would like to share our own clinical observation. In an observational application, when a physician ordered “morphine administration” for patients experiencing postoperative pain after thoracic surgery, naloxone was administered to the patient instead. Naloxone, as is known, is an opioid antagonist and not an analgesic; on the contrary, it blocks opioid effects. Despite this, a significant reduction in patients’ pain scores was observed.

This finding is important in several respects. First, it demonstrates that the placebo effect is not a weak effect and can, in the appropriate context, compete with strong analgesics. Second, it suggests that the classical “placebo analgesia = endorphin release” model may not be sufficient in all cases. Because analgesia occurred despite the administration of an agent that should theoretically block endorphin effects. This suggests that expectation can produce analgesia through pathways independent of the opioid system, that naloxone may have complex context- and dose-dependent effects, and that placebo analgesia is a heterogeneous phenomenon. Therefore, reducing the placebo effect to a single biochemical mechanism is not appropriate.

One of the most striking aspects of the placebo effect is that the physical characteristics of a drug can influence clinical outcomes. The color, size, shape, whether it is a capsule or tablet, and whether it is administered by injection can significantly affect the patient’s response to treatment. Injections are generally perceived as more powerful than tablets and produce a higher placebo effect. Capsules may be perceived as more effective than tablets. Large tablets and very small tablets may create a stronger impression. Color is also an important factor; red and yellow tones are perceived as more stimulating, while blue and green tones are perceived as more sedative (10).

These effects are not pharmacological but are based on cognitive and cultural factors. Therefore, the patient responds not to the drug itself, but to the meaning that the drug represents.

EVERY DRUG IS ALSO A PLACEBO

At this point, it is necessary to draw attention to an important phenomenon frequently observed in clinical practice. Especially in patients with chronic pain, when it is reported that the effect of a drug containing the same active substance and dose diminishes over time, it is often observed that switching to another brand name drug containing the same active substance can restore effectiveness.

Despite no pharmacological change, the alteration in clinical response demonstrates that the effect of a drug is related not only to the molecule it contains but also to the meaning attributed to it by the patient. The name of the drug, its appearance, previous experiences, and the way the physician presents the drug can directly influence the treatment response.

This observation reveals an important reality: every drug is also a placebo. That is, every pharmacological treatment carries, in addition to its specific effect, a strong contextual and expectation-related effect. Therefore, clinical efficacy should be evaluated not only in terms of the active substance but also in terms of how the treatment is presented.

Who administers the treatment and in what environment also significantly influences the outcome. Treatment provided by a healthcare professional with higher authority may create stronger expectations. Similarly, the hospital environment creates a more serious and effective treatment perception compared to outpatient settings. White coats, monitors, IV lines, and medical devices are part of the treatment and are often as effective as the drug itself.

The nocebo effect, considered the opposite of placebo, is also of great clinical importance. Negative expectations can lead to real and measurable side effects (11). This once again demonstrates the decisive role of physician–patient communication in treatment outcomes.

Particularly, emphasizing potential side effects to the patient may actually lead to their occurrence. It is known that even in placebo groups of clinical trials, side effects such as headache, nausea, and fatigue are reported at high rates. A significant portion of muscle pain observed in patients using statins has been shown to be associated with the nocebo effect (13). Similarly, patients who develop nausea and vomiting solely due to expectation before receiving chemotherapy represent one of the most striking examples of the nocebo effect.

This clearly shows that the language and communication style used by the physician can produce direct biological outcomes.

The topic of placebo is as scientifically complex as it is ethically challenging. The fundamental issue is that placebo use often involves deliberately misleading the patient. This conflicts with core ethical principles such as autonomy, truthfulness, and informed consent. The Declaration of Helsinki published by the World Medical Association has placed limits on the use of placebo. Accordingly, if an effective treatment exists, the use of placebo is restricted, and avoiding harm to the patient is essential. CIOMS and ICH guidelines similarly regulate placebo use.

Can placebo be used as a therapeutic tool?

Is placebo merely a research tool, or can it be used directly for treatment? This question constitutes the most critical and uncomfortable aspect of the placebo debate. While classical medical approaches accept placebo as part of clinical research, they approach its use in daily clinical practice with caution. However, real clinical life is not so clear-cut.

Survey studies conducted in the United States show that a significant proportion of physicians use placebo-like approaches in clinical practice. This use often does not take the form of inert substances but rather as practices referred to as “impure placebo.” For example, vitamins, low-efficacy analgesics, or drugs not appropriate for a specific indication may be used to manage patient expectations or control symptoms in cases that do not require strong pharmacological treatment.

In contrast, the administration of completely inert substances (such as sugar pills or saline) without informing the patient is quite limited today due to serious ethical concerns.

The American Medical Association has a clear stance on this issue. The use of placebo without the patient’s knowledge is considered deceptive and is not recommended because it may undermine the physician–patient trust relationship. However, an important recent development is the concept of the “open-label placebo.” In this approach, the patient is explicitly informed that the treatment is a placebo, yet it is stated that it may still provide clinical benefit. Interestingly, even such transparent applications can produce meaningful clinical responses in some cases. This finding shows that the placebo effect is not solely dependent on deception, but that expectation and meaning themselves can be therapeutic.

In a patient with chronic insomnia, specially prepared vitamin tablets were administered under the statement “I am giving you a new sleep medication,” and a significant clinical improvement was observed. This suggests that placebo may be considered as an alternative approach, especially in cases involving drugs with high dependence potential (such as benzodiazepines or sedative-hypnotics).

The fundamental question here is: Is it acceptable to mislead a patient in order to improve their condition? There is no definitive answer to this question. However, the modern ethical approach recommends not completely rejecting placebo but understanding its effects and using it as transparently as possible. Open-label placebo applications provide an important intermediate solution in this regard.

In conclusion, placebo is a tool that can provide clinical benefit when used appropriately; however, the boundaries of its use must be clearly defined. Placebo should not replace effective treatment, should not harm the patient, and should be applied in accordance with the principle of transparency whenever possible. Otherwise, placebo may cease to be a therapeutic tool and instead become a practice that undermines the trust relationship that forms the foundation of medicine.

Therefore, the modern approach is not to reject placebo entirely, but to understand and manage it within ethical boundaries. Open-label placebo studies have shown that clinical benefit can be achieved even when patients are explicitly informed that they are receiving a placebo. This finding demonstrates that the placebo effect is not solely dependent on deception, but that meaning and expectation themselves can be therapeutic.

In conclusion, placebo is one of the most disturbing yet instructive concepts in medicine. This concept teaches us that treatment is not merely about molecules. Expectation, meaning, context, and communication are at least as powerful as drugs. And sometimes, even when we think we are giving nothing, we may still be treating the patient.

REFERENCES

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Note: AI support was used in the preparation of this article.