Placebo effect in animals: what is it and why does it appear?

Although they do not have our capacity for abstract thought, they can benefit from placebo.

The placebo effect is a phenomenon that we generally tend to relate to human beings, since in order for it to be possible, it is necessary the existence of certain cognitive capacities that we generally assume do not exist in other beings. For this effect to occur, it is essential to have the perception or idea that a specific stimulation is going to generate a specific effect on a specific problem, something that requires a complex processing of both internal and external information.

However, the truth is that we are not the only beings that have shown to benefit from this effect. That is, there is the placebo effect in animalsThis is the subject we are going to talk about in this article.

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 placebo effect.

The placebo effect is understood as that situation in which an individual with a given problem presents an improvement in symptomatology that is attributed to the effects of a supposed medication or treatment that is believed to produce such improvement, despite the fact that in reality the treatment itself has no therapeutic effect on the problem..

We would be then before an improvement generated by autosuggestion, before the belief that following the treatment has or is going to produce some concrete effects on our health. It is not an illusion or a false perception.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.

• You may be interested in "What is the placebo effect and how does it work?"

Why is it considered to be specific to human beings?

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

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

The placebo effect in animals

The large number of cognitive capacities that are assumed to be necessary and indispensable for the placebo effect to emerge clashes head-on with the traditional perspective that sees the rest of the cognitive capacities of animals as being necessary and indispensable for the placebo effect to emerge. the traditional perspective that sees the rest of animals as beings with lesser cognitive capacities, which is the reason why the placebo effect is not used in animals.This is the reason why it is not generally considered that it can occur in animals. But the truth is that it does.

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

In situations where one group of animals was treated for a particular disease with a drug and others with placebo, improvements were observed in both groups (obviously greater 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 multiple disorders in which this effect can be observed, and it can even generate slowdowns in the growth of tumors.

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

Classical conditioning theory

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

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

The same happens with animals: if swallowing a pill is repeatedly associated with feeling better, the pain isIn other situations where the animal is unwell, it may expect such an effect from a pill. This does not mean that they will swallow it (variables such as whether they dislike the bad taste or texture, or relate the pill to their owner forcing them to swallow it would come into play).

Cognitive model: expectations

Probably the model that has been most difficult to apply to non-human animals is the one that refers to expectations, which are linked to a symbolic capacity that animals are not considered to possess. However, even though the cognitive capacity of each species is different, it has been observed in different beings that it is possible to create expectations and sensations of capacity to control or not to control situations, as well as the existence of learning in the face ofas well as the existence of learning in the face of 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 expects that one's own behavior will have no effect. This is typical in depressed subjects (both humans and animals), 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 capacity to recover from illness.

The effect of stress

Another possible reason for the appearance of the placebo effect is the reduction of stress in the face of illness. The fact of taking a drug or the activities or treatments that are carried out during a treatment (including the fact of trying to pet them, calm them, etc.) can reduce the stress level of the animals that follow them. Given that stress has been shown to be an important risk factor and worsens the condition of ill subjects, treatment could alleviate stress, treatment could generate a relief of such stress, which in turn in turn generate a symptomatological improvement.

This effect would also be linked to an effect that has also been observed: positive physical contact with an animal generates a more resistant state of health 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.

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

In humans, 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, and although many animals also possess these substances in their nervous systems, little evidence has been carried out in this regard, so it is only theoretical.

Placebo by proxy

The placebo effect in animals exists and has been demonstrated, but the truth is that it has also been observed that in some cases, as we have hinted above, a situation can occur in which something that is not a placebo effect is interpreted as a placebo effect, which 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 it is a placebo. the people observing it do believe that this has occurred because they have been given a particular treatment..

This type of placebo occurs especially in pet owners, who are reassured by having 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 its condition.

Another situation could be the other way around: a sick pet, perceiving that its human companion is nervous or upset about its condition, could become more uneasy and upset than its problem would cause it to be. By receiving treatment and reassuring the human in charge, such reassurance could relax the pet's nervousness.This tranquilization could relax the animal's state of alteration and also produce an improvement. We would be dealing with a somewhat different type of placebo.

Bibliographical references:

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