[Stress and allostasis: problems, outlooks and relationships]

Concepts of stress and allostasis are discussed in the paper in their interrelation and interpenetration. General adaptation syndrome is considered in the historical aspect of Claude Bernard's, William Cannon's and Hans Selye's contributions to the field, and from the standpoint of an interdisciplinary approach. Key challenges and contradictions of the stress concept are disclosed and discussed. First, the terminology ones, since this term might be understood as stress response, stressor, state of the organism and even the consequences of stress itself. Second, it is ambivalent and contradictory nature of the stress response. From the perception of stress as a reaction to the strong negative impact of environment, researchers became to divide stress onto two types: distress as a non-specific basis of disease, and eustress as a favorable factor that extends the adaptability of human organism. The third problem is connected to the interdisciplinary nature of the stress response, the effects of which being manifested in, at least, four areas: physiology, behavior, subjective experience, and cognitive functions. Particularily, physiologists are very often ignored of a role of cognitive factors in their stress research. The authors in terms of the allostasis theory, more complex adaptation process than homeostasis, resolve contradictories of stress conception observed. The paper proposes a model of allostatic states to describe distress and eustress phenomena.