Why evolution hasn't eradicated depression

It seems logical that evolution and natural selection get rid of everything unnecessary, and even more so harmful. But then it is not clear why our ancestors passed on to us a tendency to depression, and did not part with it back in the days of mammoths.

Scientists are also concerned about this issue. Biologists, psychologists, and anthropologists have developed several hypotheses to explain depression as a function of evolution. Perhaps the symptoms of the disease helpedL. E. O. Kennair, T. H. Kleppestø, S. M. Larsen et al. Depression: Is rumination really adaptive? / T. K. Shackelford, V. Zeigler-Hill. The evolution of psychopathology a person to adapt and survive. Let's try to figure it out.

How Scientists Explain Depression From an Evolutionary Perspective

So far, all these are just theories, and not necessarily compatible with each other. And some researchers do not even consider depression as a way of adaptation.

It helps to stop useless and dangerous activities.

Some scientists suggest that strong negative emotions, including those caused by depression, sometimes increased the chances of our ancestors for survival. So, due to disappointment or despondency, a person could refuseR. M. Nesse. Is Depression an Adaptation? / Archives of General Psychiatry from activities that are too dangerous or time consuming with a low chance of success.

For example, even the most skilled hunter understood that it was dangerous to go on a large animal alone, and abandoned the enterprise if the relatives did not support the venture. No matter how much a person wanted to get a lot of meat or a beautiful skin, he realized that life is more expensive. Otherwise, he was most likely to die. Presumably, depression caused apathy and thus improved survival. Therefore, she overcame natural selection.

It is possible that this mechanism sometimes works unconsciously. For example, psychologists have long noticed that babies, left without a mother for a long time, stop crying and shrink into a ball, wrapping their hands around their knees.

Previously, it could save a child's life. After all, while the mother is not around, there is no one to protect the baby from predators, and therefore it is better for him to hide. It also uses less energy and nutrients. Such behavior could persist as an unconscious reaction to dangerous conditions, when any action only worsens the situation.

She helps in relationships with others.

In primitive society, expulsion from a tribe meant a painful death. One can neither hunt nor defend against enemies or predators. According to some scientists, depression was neededN. B. Allen, P. B. T. Badcock. Darwinian models of depression: A review of evolutionary accounts of mood and mood disorders / Progress in Neuro-Psychopharmacology and Biological Psychiatryto avoid conflicts. Low self-esteem and depression made the person give in and accept the opinions of others. As a result, the likelihood of staying in the tribe increased.

This mechanism manifested itself especially clearly when people found themselves at the bottom of the existing social hierarchy. Being depressed helped to reconcile 1. J. S. Price, L. Sloman, R. Gardner Jr. et al. The Social Competition Hypothesis of Depression / The British Journal of Psychiatry;
2. J. S. Price, R. Gardner Jr., D. R. Wilson et al. Territory, Rank and Mental Health: The History of an Idea / Evolutionary Psychology with the current state of affairs and not take actions that could displease others and lead to expulsion and death.

A similar thing is observed in the wild. So, the male chimpanzee leader, defeated by a stronger rival, is forced to acceptJ. S. Price. Evolutionary aspects of anxiety disorders / Dialogues in Clinical Neuroscience new status and become submissive and quiet. After that, the animal develops a state similar to depression. Passive behavior, as it were, allows the former leader to protect himself from further attacks. So, to save life and the ability to pass genes to offspring.

Roughly the same thing happened with people in primitive society. Former leaders gave way to new leaders, but survived because they did not offer resistance after defeat.

She helps you get support.

Other scientists suggestE. H. Hagen. Evolutionary Theories of Depression: A Critical Review / The Canadian Journal of Psychiatrythat depression is an extreme version of a cry for help, a way to signal problems. In a primitive society, people would not have survived without the support of others. Especially in a difficult situation, which can trigger the development of depression.

So, a person who is unable to hunt needs help. For him, an attempt at suicide or a tacit refusal to fight does not pose a big threat: he will not survive alone in any case. But in this way, a person can attract the attention of others and receive the necessary support.

It works about the sameE. H. Hagen. The Functions of Postpartum Depression / Evolution and Human Behaviorpostpartum depressionwhen the mother does not receive the necessary help from the child's father and relatives. This reaction becomes an adaptation strategy, a way to prolong the lineage.

She helps solve difficult problems.

People who are depressed are prone to think about the same events or things. Most doctors believe that such reflections are destructive, because they take all the attention of a person and prevent him from doing anything else.

However, two American scientists, Paul Andrews and Anderson Thomson Jr., took a very different view of the situation. They assumedP. W. Andrews, J. A. Thomson, Jr. The bright side of being blue: Depression as an adaptation for analyzing complex problems / Psychological Reviewthat in some cases such an obsession and concentrated contemplation necessary. The body, as it were, forces a person to concentrate on a complex problem. A depressed person does not want to have fun or communicate, which means that all his energy and time is spent on solving a key issue. That is, depression turns out to be a way of adapting to difficult situations and hypothetically helps to overcome them.

This assumption is complemented by the fact that people in a depressed mood acceptK. Au, F. Chan, D. Wang et al. Mood in foreign exchange trading: Cognitive processes and performance / Organizational Behavior and Human Decision Processes smarter decisions than their rejoicing opponents. The former, as a rule, are more likely to doubt and try to avoid unnecessary risks. The latter act decisively and think less about the consequences. This is exactly how the participants in the experiment on the influence of mood on decision-making behaved. Investors whose investments were praised began to act recklessly and err. But the people who came under criticism acted more conservatively and earned money.

It helps fight infections

In 2012, American psychiatrists analyzedC. L. Raison, A. H. Miller. The evolutionary significance of depression in Pathogen Host Defense (PATHOS-D) / Molecular Psychiatry many genomic studies of people with depression. Scientists have noticed that genes, which are associated with an increased risk of developing this psychological disorder, are also associated with an effective immune response of the body to infections.

That is, depressive alleles (different forms of a gene) are at the same time immunological alleles that respondC.-H. Lee, F. Giuliani. The Role of Inflammation in Depression and Fatigue / Frontiers in Immunology for protecting the body from pathologies. In this case, the tendency to depression becomes beneficial from the point of view of evolution: it was various infections that most actively killed the ancestors of modern people.

It is significant that "depressive" genes are more often foundC. L. Raison, A. H. Miller. The evolutionary significance of depression in Pathogen Host Defense (PATHOS-D) / Molecular Psychiatry in people who inhabit regions with a higher risk of developing infection. For example, some residents of Ghana extract water from clean wells, while others from polluted rivers. Naturally, representatives of the second group die more often from infections. That is why their body adapts to natural conditions: the river inhabitants develop the very "depressive" genes that protect against infections.

Therefore, depression may have survived through evolution as a genetic response to disease, and not as a way of social adaptation.

Does this mean depression is good for you?

No. Maybe evolution really had its own reasons for maintaining depression - scientists do not yet give an exact answer. However, such a state cannot be consideredR. M. Nesse. Is Depression an Adaptation? / Archives of General Psychiatry normal or even more useful.

Depression is a dangerous mental disorder that must be treated. Even if it was once useful, this does not mean that today it is worth letting everything go by itself.