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

The placebo effect is a phenomenon that we generally tend to associate with the human being, since as long as it is possible, the existence of certain cognitive capacities that we generally assume do not exist in others is necessary. beings. And it is that for this effect to occur, it is essential that the perception or idea that a specific stimulation is going to generate a determined effect on a determined problem, something that demands a complex processing of both internal and external information. external.

However, the truth is that we are not the only beings who have stated that they benefit from this effect. This is, there is a placebo effect in animals, a topic that we are going to talk about 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.

The placebo effect is understood to be that situation in which an individual with a certain problem presents an improvement in the symptomatology that is attributed to the effects of a supposed medication or treatment that is considered to produce said improvement, to Although

actually the treatment itself has no therapeutic effect on the problem.

We would therefore be facing an improvement generated by autosuggestion, given the belief that following the treatment has to or will produce specific effects on our health. It is not an illusion or a false perception, but that the improvement is generally real and palpable for the patient, but it is about the product of the action of the mind on the body and not of the effects of a drug or intervention concrete.

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Why is it considered typical of the human being?

Based on the previous 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 human beings: being able to imagine that a specific substance or intervention will improve us from an ailment implies identifying both the ailment as the substance/intervention and generate the belief and expectation that taking the substance will eliminate or reduce the ailment that we suffer.

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

The placebo effect in animals

The large number of cognitive abilities that are assumed to be necessary and essential for the placebo effect to emerge clashes head-on with the traditional perspective that sees other animals as beings with less cognitive abilities, being this reason that it is not generally considered that it can occur in animals. But the truth is that it does.

It has been shown experimentally 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 studies and controls.

In situations where a group of animals was treated for a specific disease with one drug and other with placebo, improvements were observed in both groups (obviously greater in the group treated with the drug real). This improvement was observed with different measures, independent of the subjective assessment of owners or veterinarians. There are multiple disorders in which this effect can be observed, and can even cause slowdowns in tumor growth.

There are multiple possible explanations for this fact, with different authors having developed various 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 indeed in humans as well, may actually be based on conditioning acquired from previous experiences: if an animal (or person) associates that taking a substance with certain characteristics has generated a specific effect on its body (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 he will tend to believe that in future occasions upgrade to.

This is something that happens in the human being when we take a pill that is given to us in a state of pain: in a short time the pain subsides. reduces because we have assimilated that said pill will do like drugs that we have previously taken (for example the typical gelocatil).

The same goes for animals: yes swallowing a pill is repeatedly associated with feeling better, in another situation in which the animal is unwell, it can expect said effect from a pill. This does not mean that they are going to swallow it (variables would come into play here, such as whether they dislike the bad taste or texture, or relate the pill to being forced by their owner).

Cognitive model: expectations

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

The most obvious example (although it would go rather the opposite of the placebo effect, the implications are the same) is that of learned helplessness: not doing anything to avoid something because it is expected that the behavior itself will have no effects. This is something typical in depressed subjects (both humans and animals), something that 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 illness.

The effect of stress

Another of the possible reasons why the placebo effect may appear is due to the reduction of stress in the face of the disease. The fact of taking a drug or the activities or treatments that are carried out throughout a treatment (including the the fact of trying to caress them, calm them, etc.) can reduce the stress level of the animals that follow. Given that stress has been shown to be an important risk factor and worsens the state of sick subjects, treatment could lead to relief from such stress which in turn generated symptomatic improvement.

This effect would also be linked to an effect that has also been observed: positive physical contact with an animal makes its state of health more resistant and improve 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 humans, it has been observed that the perception of different degrees of discomfort, pain and physical discomfort can be greatly diminished thanks to the action of endorphins or endogenous opioids.

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

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The placebo by proxy

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

This type of placebo occurs especially in 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 state.

Another situation could occur in reverse: a sick pet, perceiving that its human companion is nervous or upset at his condition, he could become restless and upset to a greater extent than his problem would allow him to. would generate. When receiving treatment and calming down the human being in charge, such calming could relax the state of alteration of the animal and also produce an improvement. We would be facing a somewhat different type of placebo.

Bibliographic references:

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