This block includes a variety of conditions and behaviour patterns of clinical significance which tend to be persistent and appear to be the expression of the individual's characteristic lifestyle and mode of relating to himself or herself and others. Some of these conditions and patterns of behaviour emerge early in the course of individual development, as a result of both constitutional factors and social experience, while others are acquired later in life. Specific personality disorders (F60.-), mixed and other personality disorders (F61.-), and enduring personality changes (F62.-) are deeply ingrained and enduring behaviour patterns, manifesting as inflexible responses to a broad range of personal and social situations. They represent extreme or significant deviations from the way in which the average individual in a given culture perceives, thinks, feels and, particularly, relates to others. Such behaviour patterns tend to be stable and to encompass multiple domains of behaviour and psychological functioning. They are frequently, but not always, associated with various degrees of subjective distress and problems of social performance.