What is Placebo Effect and How Does it Work?

The placebo effect (ep)  is a psychological phenomenon that occurs when a treatment produces a beneficial effect due to the suggestion, not the actual effect of the treatment.

Throughout the history of the human being have been created and applied multiple and different therapeutic practices that included nonspecific therapies like drugs or drugs.

Placebo effect

For example, we can refer to lizard blood, crocodile excrement, pork tooth and numerous brews that were used as remedies in Egypt. The purpose of his administration, in general, was clear: to disgust the demon who had surely entered the body of the suffering person and get thrown out of it.

If we go back in time it seems that the first descriptor of this placebo effect was Plato who warned that “a therapeutic remedy can only be effective if before administering it is subjected to the patient to an ensalmo, a really persuasive speech.”

On the other hand was Houston in 1938 who stated that the history of medicine is largely the history of the placebo effect. According to this scientist the doctor has had a very special ally, the personal relationship with the patient. The therapeutic agents through which they obtained the cures were their own people.

Since when is the placebo effect in modern medicine?

Until very recently virtually all therapeutic interventions that had repercussions on patients were a consequence of the placebo effect. In fact, at the end of the 19th century only a very small number of substances were known with effects superior to placebo. For example, quinine to treat malaria, opium as an analgesic, colchicine for gout, amyl nitrate to dilate the arteries in people with angina and aspirin.

It is curious that many procedures that do not have a specific effect on discomfort and disease continue to be used today. All this has originated due to aspects such as:

  • The limited information that the doctors have regarding the specific action, side effects, and contraindications … of many of the drugs they administer.
  • Diagnostic errors.
  • Errors of self-administration of the drugs that patients make.
  • Variable effects of drugs according to the time of the biological cycle in which they are administered.

In addition, about 40% of the drugs that we buy in pharmacies do not have proven their effectiveness in clinical trials. In fact, there is abuse of drug use in industrialized societies.

To demonstrate the efficacy of any drug, double-blind studies are usually done, in which neither the patient nor the clinician knows whether they are administering or taking the effective substance or the placebo preparation. In this way, we control the variables that surround the clinical act and that influence in an important way the result of any therapy.

There are some studies done in this regard. For example, one performed by Abramson, Jarvik, Levine, Kaufman and Hirch reported that in administering a placebo as tap water to 33 adult subjects who thought they were taking LSD , between 25 and 60% of participants showed characteristic symptoms of the reaction To lysergic acid.

Characteristics of the placebo effect

Following the investigations carried out over time regarding this effect the following characteristics have been observed.

If we refer to quantitative terms we obtain the following interesting data:

  • The placebo effect affects between 0-70% of the people, with an average of people with responses to that effect of 35%.
  • The improvement of symptoms or amount of relief is distributed between 20-70%, with an average of 50% of people who refer it applied mainly to pain.

This is especially true with regard to pain, one of the main areas of application of placebo. Although it also applies within the field of health, as in asthma , multiple sclerosis, common cold, diabetes or ulcers .

Variables of the placebo effect

As for the diversity of variables that are behind the results of placebos we can refer to those related to the professional who administers it, related to the patient, related to the relationship between professional and user, and those related to the context and The cultural framework.

With regard to the professional, we can refer to the following aspects:

Mode in which the professional interacts with the patient

If empathic and confident in the healing properties of the treatment the effect is greater. This can mean that the professional does not watch the clock when he is with the patient, or that he only initiates a prescription after clarifying the diagnosis. In addition non-verbal communication is very important, if it transmits skepticism or insecurity the effect of placebo is much less. This has also been proven with the effect of drugs, for example with tranquilizers whose effectiveness can fall from 10 to 77%.

In 1992, Skrabanek and McCormick illustrate this effect with Asher’s paradox. He goes on to say that if a doctor firmly believes in your treatment and defends it, the results you get with it will be better, your patients will find themselves better and will come to your consultation more. And where is the paradoxical phenomenon? For in that the one who can be considered as the best professional is not

Necessarily the one who knows best, but the one who thinks he knows and is able to persuade others of it.

Patient-related variables

With regard to the patient , it has been seen that people with a high need to please , those who show a low self-esteem , or those who score high in the locus of external control (locating the control of phenomena in external aspects) show a high sensitivity to EP.

As for variables such as sex, age, hypochondria, dependence or neuroticism, it has been seen that they discriminate better to those more susceptible people. The anxiety and somatic symptoms (tachycardia, nervousness, sweating hands, difficulty sleeping or distractibility) seems to be a facilitator variable, since the administration of placebo may be sufficient to eliminate, at least temporarily.

As for the doctor-patient relationship, it is necessary to base it on a clear, concise and comprehensible communication. The goal is for the patient to correctly follow the prescribed treatment guidelines and know what to do, when to do it, to know what the drug is doing and if it believes that it really has that pharmacological property. In addition, the patient relies on the expert as someone who knows his problem and knows what it is that he must do to obtain an improvement.

Context-related variables

The context is critical too. In this way, and although they appear superfluous data, the decoration of the consultation and the elements that the medical formality entails like medicines, apparatuses, books, magazines and uniformed personnel, will contribute to the placebo effect. It also influences the conviction of all clinical staff about the effectiveness of the treatment.

Variables related to placebo

As for placebo, both the size (small), the color, the taste (the less pleasant the higher the taste is), the placebo amount prescribed (ie, precise doses, take 2 vs take 2 or 3 a day ) And prescription at fixed time intervals.

Treatment regimens must be of the medical type, ie the prescription of a medication has more power than the prescription of physical exercise or diet. In general, it has been found that the more the placebo is resembled the drug, the greater its effectiveness.

Variables related to the cultural framework

As for the cultural framework, the power of Western culture has created the ideal framework for the proliferation of the use of placebos. 

Blind trust in the medicalization of diseases contributes to the majority of people having positive experiences with medicines, even though the effect of the medication is not real. For example, the flu does not improve with antibiotics, but its administration is stressed.

In any case the patient acts as a naive doctor and attributes his change of state to the drug, so that it appears as effective when in fact it has not been. “Yesterday I was under energy, I took some vitamins and then I recovered.” This is also the case in the opposite case, ie if someone ingests a drug and does not improve, it is assumed that it is because it was an inadequate preparation and you have to change it to find the good.

What explanations exist for the placebo effect?

Although many explanations have been proposed over the years, most agree on the behavioral changes and the conditioned psychophysiological responses that can be observed after the administration of the placebo.

As for the behavioral changes, we can mention the patient’s unconcern about what causes him discomfort. By ingesting the placebo, he puts his trust in the power of relief of the latter and thus relaxes, facilitating the realization of those daily activities that can and are often incompatible with the feelings of pain.

Placebo Effect

At the same time, there is a multitude of data indicating that verbal recommendations accompanying placebo products are critical. Through the language is interposed in the behavior of people, as long as the verbal suggestions describe known and possible behaviors and have the appropriate emotional tone.

With regard to biochemical changes, it has been shown that placebo causes a conditioned psychophysiological response, by virtue of which the production of endorphins and enkephalins increases. These have an important analgesic function, and antidepressant and neuroleptic properties, inducing a general improvement of the mood .

Influence of placebo on psychological treatments

Rosenthal and Frank (1956) were largely responsible for the extension of the placebo construct to psychological treatment. They suggested that psychotherapy could be compared to a placebo treatment.

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In Frank’s words “the number of achievements of a therapy is, in fact, made up of a percentage of successes that would have occurred equally if another form of therapy had been applied.” It was considered that any procedure with credibility, and applied in a socially acceptable way (Berstein and Neitzel, 1977), would probably produce some improvement, and this was the reason why these placebos effects should be controlled.

From behavioral approaches, placebo was considered as a variable that was not of interest in itself. The placebo effects mediated by expectations did not fit into the behaviorist worldview where cognitions were considered a fiction, and thought was left out of the chains linking events with their consequences within the real world. With the emergence of cognitive-behavioral models, it began to be argued that placebo as a cognitive variable could be of interest (Kirsh, 1978).

Based on the placebo effect, treatments can be successful in two ways:

Directly, through an anxiety reducing mechanism and the consequent result of a biochemical state of the internal environment that favors and makes possible the self-healing action of the organism itself.

Indirectly, through an increase in expectations of patient’s efficacy, which affect the onset and persistence of their coping behaviors of the disorder or disease.

With respect to the verification of the efficacy of psychological treatments, Hersen and Barlow concluded that research should focus on the realization of series of intrasubject systematic replications, so that it is possible to discover for a specific treatment what variables of the patient, therapist and Situation are critical to your success. Thus homogeneous population groups could be built on which to investigate later.


After making a tour from the beginning of the study of the placebo effect to the present and the application that is given, we could infer that in reality, current therapies do not have to have a greater degree of effectiveness than faith in healing Or the rituals of primitive societies.

However, it is true that everything has to be contextualized, and what in one culture can be seen as scientific, in others can be magic or superstitious.

The power of the human mind continues to surprise us and undoubtedly there are still things to discover and that will bring us closer to a degree of reality that we now consider unthinkable.

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