Oppression of mental and emotional state in ARVI and cold can be caused by chemical signals sent by the immune system to the brain centers.
Everyone knows an unpleasant condition with any cold - after all, many are concerned not so much with a cough or runny nose, as a sharp decline in activity in the form of apathy, fatigue, the inability to concentrate. Try to explain this situation with the phrase "the disease takes away all the forces" is meaningless. After all, not only physical possibilities disappear: mental activity becomes complicated, emotions are leveled, the psyche becomes oppressed.
Probably, the disease has some effect on brain activity? Or the reason for the activity of the immune system?
Dr. Thomas Blank and his team conducted a series of studies with rodents suffering from a non-long-term viral infection. Since scientists sought to assess the behavior and mental characteristics of mice, special testing was initiated: the diseased animals were put into a water tank, from which it was difficult for them to get out on their own. What did the researchers see?
Healthy rodents continually repeated attempts to get out of the tank. A sick mouse quickly completed the fight and spent their energy just to stay afloat and not drown.
According to scientists, with the onset of the infectious process, the immunity of animals stimulated the production of beta-interferon, a specific antiviral agent. This substance is able to come into contact with the cellular receptors that make up the blood-brain barrier. With the disabling of the receptor data, the mice became more resistant to the apathy state associated with the disease.
If we consider the situation at the molecular-cellular level, we can describe it like this: when the infection was introduced, the immune defense stimulated beta-interferon, which acts on the receptors of the vessels, and activates the production of the immunoprotein CXCL10. This protein belongs to the group of cytokines and weakens the properties of the nerve cells of the hippocampus. However, we must not forget that there are other variants of the immune response, in which interferon with its antiviral properties is not needed - for example, it is an inflammatory process caused by microbes. Apparently, here work any other mechanisms that cause apathy, drowsiness and loss of efficiency.
From the point of view of evolution, the situation is clear: psychological lethargy leads to energy savings, because energy is necessary for the patient to fight the disease. However, scientists would like to learn how to manage immune signals that provoke the development of "colds" - because today people do not need to so cherish their energy, as it was a hundred thousand years ago.
In addition, similar signs of depression are also found in patients with oncology and autoimmune diseases, so solving this problem would help to answer other similar questions.