History of Medicine: the Placebo Effect

It is not new that we know that an inert drug can trigger beneficial responses to an individual’s health – this is the famous placebo effect.

Just as a curiosity, there is also the nocebo effect, which is that in which an individual feels some adverse effect of an inert substance, that is, that would not be able to cause that effect.

More and more studies are being developed to try to understand where this effect comes from and its importance for Medicine.

As a further curiosity, according to the medical dictionary Hooper, “placebo” comes from the Latin placere which means “I will please”. It even fits, doesn’t it?

Doctors Arthur and Elaine Shapiro write: “The treatment landscape, since antiquity, provides ample support for the belief that, until recently, the history of medical treatment is essentially the history of the placebo effect…

For example, the first three editions of London Pharmacopoeia , published in the 17th century, included inert drugs, such as skull moss from dead victims of violent death and plaster from Vigo (including viper meat, live frogs and worms). ”


The “discovery” of the placebo effect occurred in the year 1796, when the American physician Elisha Perkins patented a device composed of two metal rods that, if agitated around the patient, had the ability to eliminate the harmful electrical fluid (according to the doctor , was the cause of all the suffering). He called it “Perkins Tractor”.

The beneficial effect of this device drew the attention of the physician John Haygarth, who, after studies and well-controlled experiments, managed to prove that the results of the treatment carried out with Tractor Perkins were true (that is, they improved the clinic of the patients), however, the same effect it was also hit with a replica of the device made of wood.

Thus, Haygarth was the first doctor to demonstrate that it is possible to obtain positive responses in treatments for patients with inert or “ineffective” procedures, now known as the Placebo Effect.

Many believe that such an effect occurs secondarily to a psychological effect, due to a real effect caused by belief or a subjective illusion, that is, if I believe that a pill helps me, it will help. Or the physical condition doesn’t change, but I feel changed.

In a study published in 1999, Kirsch and Guy Sapirstein (Pavloviano) analyzed 19 clinical trials of antidepressants and came to the conclusion that the expectation of improvement, rather than changes in neurotransmitters, was responsible for 75% of the drugs’ effectiveness.


There are several scientific currents to try to explain this effect. The two main ones will be mentioned below:

– Classic or Pavlovian conditioning: defends that it is an unconscious response in which the physiological conditions adapt to the “medicine”. For example, when a placebo is administered for the first time, we will have a limited effect. As the medication is administered more often, the responses also become better.

Another way can be an active drug being administered over a period of time (eg: 5 days) and, after that period, the patient starts to receive the placebo, however the organism continues to maintain the desired response. In this case, if the patient finds out he is taking something without the active ingredient, the treatment will stop working.

– Two-part conscious mechanism:

. Expectation of reward: in this case, the patient’s expectation that his situation will improve activates the cerebral rewards network (nucleus accumbens), contributing to recovery, since the individual will be more motivated to carry out the treatment;

. Anxiety modulation: the patient responds to the treatment in a conscious way, since the response is coming from the psychological. The answer occurs by a combination of the physiological and the conscious.


Yes! It can be divided into inert or active. The first type is one in which there is no pharmacological action. For example: sugar or flour pills.

The active placebo, on the other hand, is one that has an active principle (as the name implies), but it is not used for its intended purpose. For example, a vitamin C pill can relieve an individual’s muscle pain if they believe they are taking a pain reliever.


Well, guys! It is important to always be honest with patients. As a result, no matter how much the placebo effect exists, and is beneficial in several situations, it is not fair, nor ethical, to treat people with harmless procedures and / or medications, without them being aware of this fact.


In 1955, American physician Henry Beecher documented the famous case of soldiers in World War II, who experienced major pain relief when they received injections of saline solutions, when supplies of morphine were no longer available (including one of the mechanisms of placebo effect seems to involve endogenous opioids, in addition to dopamine activity).


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