Possible mechanisms of the effects exerted by stress (in the broad sense of the term) on the human genome and manifested in modifications of behavior are described in this review. Behavioral epigenetics opens new prospects for interpretation of the evolution of behavior induced by changes in living conditions. Epigenetic labels (imprints, methylation of DNA and/or covalent modifications of histones) appear under the influence of actual stress environmental influences, including social interactions. The appearance of such labels is not random; it is determined contextually and leads to behavioral disorders that can be transmitted through future generations. Stress phenomena of modern life, which are psychosocial in their nature, realize their effects via quite definite biological mechanisms. Epigenetic modifications are the most probable candidates for the role of relatively fast genetic mechanisms determining changes in behavior and mental health of great contingents of individuals living under contemporary conditions of ever-increasing stress loading.