Human activity in conditions of extreme influence of environmental factors is accompanied by a long-term stressful state, which modifies the course of adaptation and provokes maladaptation disorders with the subsequent development of pathology. At the same time, maladaptive disorders do not have specific manifestations, which complicates diagnosis. In order to determine the specifics of changes in psychophysiological functions under the influence of extreme factors, medical and psychophysiological studies were performed with the participation of Antarctic winterers and persons with post-traumatic stress disorders. A number of new and modified methods of research of the psychophysiological state, which were used in the monitoring mode during the year of wintering, were involved. The diagnostic and prognostic effectiveness of certain characteristic changes in indicators of electrical activity of the brain, maintenance of statokinetic stability (assessment of central regulation mechanisms), psycho-emotional color preference (assessment of psychophysical tone) and individual genetic features (polymorphism of the hypoxia-inducible factor 1α gene) has been established. The practical application of psychophysiological state assessment indicators in the system of medical and psychological support of Antarctic expeditions has shown their diagnostic and prognostic effectiveness.