Japan scientists have found that Herpes virus 6 causes depression. This virus is dormant in the human organism and causes disease by reacting to a high-level of stress. The scientists consider that the study of the activation mechanism of this virus allows for more effective diagnosis and treatment in the early stages of depression. Scientists of the Jikei University School of Medicine have studied human herpesvirus type 6 (there are a total of 8 herpes viruses). A neurotropic virus is spread all over the world (100% of people carry this virus). The virus hides in the blood and maintains a state of the latent infection in the carrier. When a person is stressed or very tired, the virus becomes thicker and can be found in saliva. Then it enters the olfactory bulb through the nose and infects it. The SITH-1 gene in the virus synthesizes the SITH-1 protein. It, in turn, directs calcium to the onion cells and kills them. Although the main function of the olfactory bulb is to perceive odors, it also affects a person's emotions. Therefore, if its functions are impaired, stress increases and the brain reacts to it, causing depression. SITH-1 was found in 80% of people suffering from depression. This means that if a person has a high concentration of this protein in their blood, they are more likely to get sick (12 times). This protein can always be detected in people in a bad mood and can be diagnosed in the early stages of the disease. Additional research is needed to determine the mechanism of the disease and to find a cure.