Can animals have depression?
Can animals develop depression? Extrapolating mental disorders to animals but based on human criteria is something that may not be entirely accurate.
However, it has been possible to see behaviors in animals that would coincide with psychopathology that, until now, was diagnosed in humans.
The question is very complex, and we will address it below, trying to give a well-documented answer as to whether it is possible for animals to suffer from depressive symptoms.
Is it possible for an animal to develop depression?
In the same way that human beings can present a wide repertoire of psychological problems, which have a negative impact on our well-being, it has been seen that many animals, especially mammals, can also suffer from psychopathology.
However, the study of animal psychopathology is a very complex issue , without being able to say with a resounding “yes” that animals suffer from mental disorders. The reason for this is that the conception of current mental disorders has been made on the basis of what is understood by being a human being adjusted in vital aspects such as family, social relations, work/study, and others. These aspects, as you can understand, are not all found in other species.
So, since depression is understood as a set of human symptoms based on human criteria , how is it possible to diagnose it in other animals? The DSM and ICD criteria can be helpful in trying to give an animal a diagnostic label, but it can never be overlooked that such a diagnosis would not be comprehensive or entirely accurate for the ‘patient’ who has been given it.
Taking all this into account, in the following sections we will try to give a better explained answer about why animals can have depression, but always taking into account that the way depressive symptoms are seen in non-human animals should be considered as provisional.
Animals and humans: can they be compared?
Human beings have a wide repertoire of behaviours. Some of them are healthy, providing us with well-being and a correct social adjustment, while others are harmful, bringing us all kinds of psychological problems, or are caused by a psychological problem behind them.
Trying to see whether or not animals have mental disorders, and especially depression, is really complicated, since the researcher who carries out the study that addresses this issue will not be able to dissociate himself from his human conception of psychopathology. Interpreting depression in animals will always be done, whether we want it or not, from a human perspective .
Despite the difficulty of extrapolating human mental disorders to animals, it is curious how most research on psychopathology has been done using animal models. The idea behind this type of research, which often takes an evolutionary view, is that the brain mechanisms seen in humans are shared in other species as well. This would mean that neurological problems in animals could be replicated in humans.
It is complicated to think that there are animals that can have depression but, ironically, many antidepressant drugs have been tested on animals, seeing how brain structures homologous to ours work in the absence or presence of neurotransmitters such as dopamine and serotonin, which are involved in depression.
Many neurologists and neurosurgeons, such as Philip R. Weinstein, maintain that many brain structures are shared by several species of vertebrates, especially among mammals . These structures perform, in the vast majority of cases, similar functions. Of these, the brains of several species of primates, such as chimpanzees, are particularly noteworthy.
The case of animals in captivity
When studying depression in other species, the most studied have been animals that have been bred in captivity, especially in places where they have had little space, have suffered abuse and have not been able to perform their species’ behaviour in the wild.
The debate on animal experimentation is as hot a topic as the existence of zoos and circuses . Researchers, for better or worse, have at their disposal animals with which they can carry out situations such as sensory deprivation, forced separation and limitation of food. Although all animal experimentation is done with an objective and must pass an ethics committee
However, one situation where ethics is conspicuous by its absence is in animal shows, especially in circuses and zoos with few scruples. This should not be interpreted as a generalisation, since we are not saying that all animal shows are abusive. Zoos carry out an impeccable species conservation task in most cases, and many circus companies are releasing their animal performers.
Unfortunately, many of the animals in this type of places suffer from mistreatment, they are subjected to hard training that involves great physical, psychological and emotional stress , and this causes deep wounds in their mental health, which will end up manifesting itself in the form of behavioral problems, depression and anxiety.
However, regardless of whether there is abuse or not, what should be understood about these animals is that they are not in their habitat. They do not develop in the same way as animals belonging to the same species would in the wild. This means that, not being able to show their true nature, confined to a few square meters, they are forced to reserve their energies, which sooner or later will emerge to the surface in very varied forms.
Due to this, and especially in very mistreated animals, which end up showing unhealthy behaviours, such as self-injury, pulling out their hair or feathers , scratching themselves until blood comes out, as well as showing themselves to be apathetic, with acquired helplessness and nervousness.
How do you know if an animal is depressed?
When we talk about depression in animals, many people have the preconceived idea that the symptoms associated with this mood disorder will manifest themselves in more or less the same way in all species. This is not the case. Just as animals have different plumage and fur, eat a variety of things and play a different role in the food chain, their depressive behaviors will also be variable depending on the species.
However, it has not been possible to study all animal species in the world , nor is it conceivable that certain species, such as corals or barnacles, may have depression as we understand it behaviourally. Most of the research has focused on mammals, especially chimpanzees and pets such as dogs and cats.
Within the field of primatology, although many apes have shown much greater language skills than other animals, it can be said that their linguistic ability is limited. It does not allow them to reveal their internal world, a fundamental aspect in the diagnosis of depression with people, since it is important to know how they live their problems.
Most researchers with chimpanzees use observation to learn about their mental health. While observing them, they look at their social behaviour, their sexual interest, what their motivation is in front of the food , if they decide to face a potentially deadly threat, if they separate from the group and if their sleeping patterns have been altered without an apparent environmental cause.
An example of chimpanzee depression is the case of Flint, a chimpanzee who was studied by primatologist Jane Goodall in Gombe National Park in Tanzania and can be read in her book Through a window (1990).
Flint lived with his mother until she passed away. From then on, he started a period of mourning, isolating himself from the rest of the chimpanzees and staying still looking at the infinite, without eating anything at all. She never stopped looking towards the horizon, hoping that her mother would return. Meanwhile, she gradually became weaker and weaker until she finally died of starvation.
Leaving aside the chimps, we move on to pets, especially dogs. Veterinarians usually see dogs that manifest all kinds of behaviours when their owners leave the house, showing separation anxiety, crying, howling and behaving in a very impulsive way . They have also seen self-harm, such as scratching until they bleed and knocking on the door so violently that they hurt themselves. There are even dogs who, being depressed, start hunting imaginary flies.
As for cats, when they are very depressed, they do just the opposite of dogs: they stay still, immobile, afraid to make any movement.
- Brent L, Lee DR, Eichberg JW (1989) The effects of single caging on chimpanzee behavior. Lab Anim Sci 39: pp. 345 – 346.
- Koob GF, Ehlers CL, Kupfers DJ, editors. (1989) Animal models of depression. New York: Springer-Verlag. 300 p.
- Harlow HF, Dodsworth RO, Harlow MK (1965) Total social isolation in monkeys. Proc Natl Acad Sci U S A 54: pp. 90 – 97.