The aim of the study was to study the characteristics of the prevalence, dynamics and pathomorphism of borderline mental pathology in students of adolescence and youth. Research methods - clinical examination, longitudinal monitoring and retrospective analysis. With the participation of a psychiatrist, on the basis of informed consent, 1,300 adolescents aged 15-19 years were examined between 1986 -2019. According to a 2018-2019 study, a
high prevalence of boundary mental pathology is provided in article. Frequency of occurrence of violations was 67% Data on high prevalence of boundary mental pathology are provided in article. Frequency of occurrence of violations was 67%. Data from a retrospective study showing a pronounced increase in the prevalence of neurosis are presented. The results of a comparative longitudinal study prove a more favorable course of pre-painful mental disorders in adolescence (16-17 years old) than among students 18-19 years old. The pathomorphism of the clinical significance of a number of behavioral deviations in the historical interval of 40 years is described. Based on the studies, the basic principles of psychoprophylaxis in students of adolescents are formulated.