The article examines the psychological and psychiatric aspects of unusual living conditions caused by the pandemic of the novel coronavirus infection COVID-19. The features of the formation of psychopathological disorders in the population during an unfavorable epidemiological situation are analyzed. Five periods of their development are identified, which were characterized by their specific features depending on the influence of various factors (patterns of development of the infectious process, the nature of its information support, organizational measures taken, etc.). In the study of the psychological and pathopsychological characteristics of the response under conditions of an unfavorable epidemiological situation, it was established that their structure and clinical features had, along with the general patterns (characteristic for each of the periods of the development of the epidemic situation), a number of specific features. In the course of studying the psychological and psychiatric aspects of unusual conditions of existence (forced self-isolation), three groups of people were identified, according to their age and the nature of their professional activities. It was established that the psychological forms of response and the features of psychopathological manifestations in the conditions of an unfavorable epidemiological situation caused by COVID-19 were characterized by heterogeneity and polymorphism and were determined both by the course of the epidemic process and by the influence of various biomedical, socio-psychological, informational, and professional household pathogenic factors. Of particular importance was the fact that the degree of influence of these factors on the mental health of people was largely determined by the gradually increasing asteniс effect of each of them (the “vicious circle”), with the formation of a “favorable asthenic soil” that promotes the development of more marked and persistent mental and psychosomatic disorders.