ABSTRACT
Personality disorders are odd. They are common (affecting around 7-10% of the population1,2), have a major influence on society3 and yet are almost universally neglected in ordinary psychiatric practice. It is also odd that they are the least stable diagnoses in psychiatric practice4 and yet regarded as conditions that are stable, arising in late adolescence and persisting to late middle or old age. This is also an essential element in their general description: people with personality disorder have an ‘enduring pattern of inner experience and behaviour that deviates markedly from the expectations of the individual’s culture’.5 This dissonance between the notional lay impression of personality as the bedrock of psychic functioning that make the person’s sense of ‘self’, and empirical data that suggest the diagnosis is unstable, is one of the major puzzles behind the diagnosis, and perhaps helps to explain why its measurement is such a perennial issue for psychiatrists and psychologists within and outside the research area. This is why researchers and clinicians are very much involved in questioning the reliability of personality disorder, and in this context the lay meaning of ‘reliable’ becomes the same as the statistical one of agreement. If people cannot agree on what constitutes personality disorder, then there is little confidence in those who are diagnosed as having the condition. For psychiatrists in training, it is important to start with the existing classification, to explain why it fails and what is likely to be offered as an alternative that is better suited to clinical practice. The course and treatment of these conditions is then discussed in the light of both new and old classifications, and readers can then come to their own conclusions as to which is superior.
