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Placebo effect in animals: what it is and why it appears

Placebo effect in animals: what it is and why it appears

March 24, 2024

The placebo effect is a phenomenon that we usually tend to relate to the human being, because as long as this is possible is necessary the existence of certain cognitive abilities that we generally assume nonexistent in other beings. And is that for this effect is essential to be the perception or idea that a specific stimulation will generate a particular effect on a particular problem, something that requires a complex processing of information both internally and externally.

However, the truth is that we are not the only beings that have expressed benefit from this effect. This is, there is a placebo effect in animals , topic of which we are going to talk throughout this article.


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What is the placebo effect?

Before delving into the possibility of finding the placebo effect in non-human animals, it is necessary to briefly clarify what we call the placebo effect.

A placebo effect is understood as the situation in which an individual with a certain problem has an improvement in the symptoms that is attributed to the effects of a supposed medication or treatment that is considered to produce such improvement, despite the fact that in fact the treatment itself has no therapeutic effect on the problem .

We would therefore be in the face of an improvement generated by autosuggestion, given the belief that the follow-up of treatment has or will produce specific effects on our health. It is not an illusion or a false perception , but the improvement is usually real and palpable for the patient, but it is the product of the action of the mind on the body and not the effects of a specific drug or intervention.


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Why is it considered proper to the human being?

Based on the above definition, we can come to understand why at the popular level we tend to think of the placebo effect as something specific and unique in the human being: to be able to imagine that a substance or concrete intervention will improve us of a disease implies identify both the ailment and the substance / intervention and generate the belief and expectation that the taking of the substance will eliminate or reduce the ailment that we suffer.

This is, it requires a certain capacity for imagination, planning and abstraction at the time of projecting positive properties to the substance itself for the specific situation in which we are. It also requires the ability to make expectations about the possibility of recovery.


The placebo effect in animals

The large number of cognitive abilities that are supposed to be necessary and essential for the placebo effect to arise clashes head-on with the traditional perspective that sees the rest of animals as beings with lower cognitive abilities This being the reason why it is not generally considered that it could occur in animals. But the truth is that it does.

It has been demonstrated experimentally with different animals, including dogs, that the supply of certain care and completely innocuous substances can generate a positive effect on the immune system, through case-control studies.

In situations where a group of animals was treated for a specific disease with a drug and others with placebo, improvements were observed in both groups (obviously higher in the group treated with the real drug). This improvement was objectified with different measures, independent of the subjective assessment of owners or veterinarians . There are many disorders in which this effect can be observed, and may even generate slowdowns in the growth of tumors.

There are many possible explanations for this fact, with different authors having elaborated different theories and models in this regard. The following are some of them, being especially in the first two cases some of the most accepted.

The theory of classical conditioning

The causes of the placebo effect in animals, and in fact also in humans, can actually be based on the conditioning acquired from previous experiences : if an animal (or person) associates that taking a substance with certain characteristics has generated a specific effect in its organism (for example, feeling more calm after drinking a liquid of a certain color or taking something similar to a pill), the subject in question, he will get to assimilate the improvement with the stimulation in such a way that he will tend to believe that in future occasions he will improve.

This is something that happens in humans when we take a pill that gives us in a state of pain: in a short time the pain is reduced because we have assimilated that this pill will do as drugs that we have previously taken (for example the typical Gelocatil).

The same goes for animals: yes Swallowing a pill is repeatedly associated with being better , in another situation in which the animal is found to be bad, it can wait for this effect of a pill. This does not mean that they are going to swallow it (in this variable would come into play as if they dislike the bad taste or texture, or relate the pill that the owner requires).

Cognitive model: expectations

Probably the model that has had more difficulty to apply with non-human animals is the one that refers to the expectations, being these something linked to a symbolic capacity that is considered that the animals do not possess. However, although the cognitive capacity of each species is different, it has been observed in different beings that is possible create expectations and feelings of ability to control or not control situations , as well as the existence of learning before stimulation.

The most obvious example (although it would be rather the opposite of the placebo effect, the implications are the same) is that of learned helplessness: doing nothing to avoid something because one's behavior is expected to have no effect. This is typical of subjects (both humans and animals) depressed, which in turn generates a decrease in the body's defenses. The opposite situation would generate, on the contrary, an increase in the tone of the immune system and a greater ability to recover from the disease.

The effect of stress

Another possible reason why the placebo effect may appear is due to the reduction of stress to the disease. The fact of taking a drug or the activities or treatments that are carried out along a treatment (including the fact of trying to caress them, calm them, etc.) can reduce the level of stress of the animals that follow them. Since stress has manifested itself as an important risk factor and worsens the condition of sick subjects, the treatment could generate relief from this stress which in turn will generate a symptomatic improvement.

This effect would also be linked to an effect that has also been observed: positive physical contact with an animal means that its state of health is more resistant and improves the immune system, in the same way that contact with animals is usually a positive factor in the improvement of different diseases and physical and mental disorders in humans.

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A theory not yet extrapolated to animals: the role of endogenous opioids

In the human being it has been observed that the perception of different degrees of discomfort, pain and physical discomfort can be diminished to a great extent thanks to the action of endorphins or endogenous opioids .

However, although many animals also have this type of substance in their nervous systems, few tests have been carried out in this regard, so it is something theoretical.

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The placebo by proxy

The placebo effect in animals exists and it is something that is proven, but the fact is that it has also been observed that in some cases, as we have hinted earlier, a situation may occur in which a placebo effect is interpreted as something that it is not, what would be known as a placebo by proxy: the animal in question does not present a variation in its symptomatology, but the people who observe it do believe that this has occurred because they have been given specific treatment .

This type of placebo is especially given to pet owners, who are reassured that they have provided some type of treatment to their animal companion and perceive it as better than before even though there may not have been an improvement in their condition.

Another situation could be the reverse: a sick pet, perceiving that his human companion is nervous or upset with his state, could become restless and more altered than his problem would generate. When receiving a treatment and reassuring the human being to the position , said reassurance could relax the state of alteration of the animal and also produce an improvement. We would be facing a different type of placebo.

Bibliographic references:

  • McMillan, F.D. (1999) .The placebo effect in animals. JAVMA, 215 (7): 992-999.

Do Placebos Work For Animals? Yes, Weirdly Enough (March 2024).


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