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What is the placebo effect and how does it work?

What is the placebo effect and how does it work?

May 10, 2021

In our daily lives, we often take medications and undergo different treatments in order to improve our health or overcome a specific problem. On more than one occasion we have heard about the advantages of some techniques that do not enjoy scientific recognition and in spite of everything, many people seem to work for it.

Both in these cases and in many other more recognized treatments, it is legitimate to ask ourselves if what we take or do really has a real effect on our health. In other words, is the treatment I am following really effective or does the improvement itself have another explanation? Maybe we are facing a case of placebo effect . Let's see what this means and how this phenomenon is taken into account in the clinical context.


Defining a placebo

We understand as placebo effect that positive and beneficial effect produced by a placebo , element that by itself does not have a curative effect on the problem that is being treated by the mere fact of its application. That is, the substance or treatment does not have qualities that produce an improvement in the symptoms, but the fact that it is receiving a treatment leads to the belief that it will improve, which in itself causes improvement.

The placebo consideration is not limited to substances, but can also appear under psychological treatments, surgeries or other interventions.

In the case of placebo we refer to a substance, this can be a totally innocuous element (a saline solution or sugar, for example) also called pure placebo, or a substance that does have a therapeutic effect for some disease or disorder but not for the one that has been prescribed. In this second case we would be facing a pseudoplacebo.


Functioning of the placebo effect

The functioning of this phenomenon is explained at the psychological level by two basic mechanisms: classical conditioning and expectations.

First, the patient receiving the placebo has the expectation of recovering , depending on the history of learning followed throughout his life, in which an improvement usually occurs after following a treatment.

These expectations condition the response to treatment, favoring the response of recovery of health (This fact has been demonstrated in the immune response). The greater the expectation of improvement, the greater the effect of the placebo, with which the conditioning will be increasing. Of course, to work properly the first step must be successful.

Other factors that influence this psychological effect

The placebo effect is also mediated by the professionalism and sense of competence projected by the person administering it, the context in which the shot is taken, the type of problem faced and other characteristics such as cost, presentation, materials or rituals necessary to take it.


Placebos of more expensive and more elaborate appearance tend to be more effective . For example, a sugar pill is more effective as a placebo if it has a capsule shape than if it is lump-shaped. In a way, the appearance of exclusivity makes expectations about its effectiveness go up or down in parallel with this.

The neurological basis of placebo

At the neurophysiological level, it has been shown that the application of placebo stimulates the frontal cortex, the nucleus accumbens, the gray matter and the amygdala, activating the dopaminergic pathways and (to a lesser extent) the serotonergic pathway. This activation causes a feeling of reward and relaxation that coincides with the improvement perceived by patients.

Patients with pain, somatic symptoms, Parkinson's, dementia or epilepsy have benefited from the use of placebos in research environments, improving their situation. The effects are especially marked in those afflicted with pain, having greater effect the greater the placebo and the initial pain.

However, the mechanism of action of the placebo effect it remains, partly a mystery . The intriguing aspect of this process is that it seems to be a phenomenon in which abstract thought comes to influence very basic and primitive mental processes, which act in a similar way in non-human animals.

For example, it is difficult to explain that a belief could interfere with something like the processing of pain, a biological mechanism that appeared more than 100 million years ago in the evolutionary chain that leads to our species and that has been consolidating cause of its great usefulness for our survival. However, the evidence shows that the suggestion produced, for example, through hypnosis, is able to make this sensation significantly more

Appearance and application contexts

Once we have briefly explored what the placebo effect is and how it works, we should ask ourselves where this phenomenon is usually applied actively .

As we will see, the placebo effect is especially used in research, although it is also occasionally linked to clinical practice.

At the research level

The treatments that are used in clinical practice must be tested in order to verify their real effectiveness. For this, the use of a case and control methodology is frequent, in which two groups of individuals are established. One of the groups is given the treatment in question, and the second, known as a control group, is given a placebo. .

The use of a placebo in the control group allows to observe the efficacy of the treatment in question, since it allows to check whether the differences between the pretreatment and the aftercare perceived in the group receiving the treatment are due to this or to other factors external to it. .

At the clinical level

Although it involves a series of ethical conflicts, sometimes the placebo effect has been applied in clinical practice . The most frequently cited reasons have been the patient's unjustified demand for medications, or the need to calm them, or the exhaustion of other therapeutic options.

Also, many alternative therapies and homeopathic benefit from this effect, which is why despite not having mechanisms of action related to effects of real effectiveness sometimes result in some effectiveness.

Relationship with other effects

The placebo effect is related to other similar phenomena, although there are remarkable differences between them.

Hawthorne effect

The placebo effect can sometimes be confused with other types of effects. An example of this is the confusion with the Hawthorne effect. The latter refers to behavior modification when we know we are observed or evaluated (for example, when there is someone analyzing our actions, such as a superior at work or simply an external observer in a class), without the possible improvement in functioning being due to any other cause than the measurement itself.

The similarities with the placebo effect are found in the fact that in general there is a perceptible improvement in the state and vital functioning of the individual. However, the placebo effect is something totally unconscious, and is given the belief that it is really going to produce an improvement before the application of a course of treatment, while the Hawthorne effect is a form of reactivity to the knowledge that is measuring or evaluating a characteristic, situation or phenomenon.

Nocebo effect

The placebo effect has a counterpart, known as nocebo effect. In this effect the patient suffers a worsening or a side effect due to the application of a treatment or a placebo , being this inexplicable by the mechanism of action of the medicine.

Although the investigation of this phenomenon is smaller since it is less frequent, it can be explained by the same mechanisms of expectation and conditioning as placebo: it is expected that a negative symptom will occur. An example of this is the occurrence of secondary symptoms that patients have seen in a prospect even though there are no threats at the biological level.

Applied to research, the nocebo effect is also what makes studies based on replacing the control group with one of patients on the waiting list not entirely valid, since this psychological phenomenon makes these patients tend to feel worse. what they would do if they were not waiting for treatment, to keep in mind that nothing has yet been administered to cure them.

Pygmalion effect or self-fulfilling prophecy

The Pygmalion effect has a clear relationship with both the placebo effect and the previous ones. This effect is based on the fact that the expressed expectation that a certain situation or phenomenon will occur leads to the subject ending up performing actions that lead to provoking the initially expected situation. Thus, its functioning is very similar to that of the placebo effect at the cognitive level, in that the belief that it is going to improve causes its own improvement.

As a type of placebo effect, this phenomenon leads people to feel better in the expectation that this is what is expected of them.

In conclusion

You have to bear in mind that The placebo effect can be found even in treatments of proven effectiveness . A clear example can be seen in a recovery or immediate improvement before taking a medication, such as an antidepressant. Although the effectiveness of the treatment can be proven, these drugs usually take weeks to be effective, so a very early improvement may be due to the placebo effect. In this way, both this phenomenon and the healing produced by the efficacy mechanism of psychotherapy or a drug can overlap.

It is also important to keep in mind that the placebo effect it is not imaginary ; there is really an improvement in the psychic or even physical state (especially the immune and neuroendocrine system), that is, in many cases it is objectively verifiable and generates physical changes, although generally not radical ones.

On the other hand, although the usefulness of this effect has been demonstrated in some medical treatments, you have to take into account the possibility of a perverse use of it , being used with the objective of obtaining economic benefit in many "miraculous" products.

Bibliographic references:

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