Over the past 40 years in Russia there were mysterious fluctuations of total mortality. The range of amplitudes varied from 10.4‰ to 16.4‰. The number of excess victims reached 14 million people. The reasons for demographic zigzags left without understanding. The objective of the research is to identify the nature of mortality fluctuations in Russia. State demographic statistics served as the basic material for scientific research. There were used standard methods of mathematical analysis. No significant relationships were found between mortality amplitudes and traditional risk factors: smoking, hypertension, blood cholesterol, body mass index, physical inactivity, stress, poverty, and alcohol use. Therefor it was suggested an “X” factor as demographic determinant. Its properties were: high speed of synchronic propagation on vast territory, influence on most diseases, presence of positive and negative effects, age preference of middle-aged, gender selectivity in relation to men. Material agents do not have such symptoms. A hypothesis is put forward about the demographic significance of social atmosphere: aggressiveness, measured by homicide deaths, and depression, measured by suicide deaths. The correlation coefficient between them is 0,97. Half-sum of both is called the aggressive-depressive syndrome (ADS). Association of ADS with the rest of mortality had correlation coefficient 0.94 in the escalating death vector (1986-2003) and 0.96 in the descending death vector (2003-2017). This means, that at least 80% of total mortality fluctuations were caused by ADS waves of social atmosphere. Its properties correspond to the “X” factor. The sources of aggression and depression were the important socio-economic events, taken in the country. They generated the “contagious” meanings and emotions, spread through the mass media. It formed the streams of destructive or creative psychosomatic interactions. The short time between mental processes and somatic responses, including diseases, indicates the existence of ultra-rapid demographic reactions.