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.

Disorders of adult personality and behaviour that have developed in persons with no previous personality disorder following exposure to catastrophic or excessive prolonged stress, or following a severe psychiatric illness. These diagnoses should be made only when there is evidence of a definite and enduring change in a person's pattern of perceiving, relating to, or thinking about the environment and himself or herself. The personality change should be significant and be associated with inflexible and maladaptive behaviour not present before the pathogenic experience. The change should not be a direct manifestation of another mental disorder or a residual symptom of any antecedent mental disorder.