Personality disorder represents a diagnosis very different from others in psychiatry. This is because it describes a long-standing integral part of a person, not just an affliction that has happened. Because of the sensitivity of ascribing a core part of a person’s being to the impersonality of a diagnostic term, the subject has been widely stigmatised. However, the condition is very common and affects one-tenth of the population. In this chapter, the clinical features of personality disorder identified in the new ICD-11 severity classification are described and their value illustrated. A fuller description of the ICD-11 classification can be found in another College publication.

There are five levels of diagnosis of personality disorder, including the sub-syndromal form – personality difficulty – which is by far the most common. The diagnosis of borderline personality disorder is the most used in practice but is a heterogeneous term that overlaps with almost every other disorder in psychiatry. All personality disorders have approximately equal genetic and environmental precursors, and the involvement of childhood adverse experiences and trauma is unfortunately true for this as for all psychiatric disorders.