There is a natural curiosity about why some people are healthier than others. One consistent theme is that dispositional variables or personality may predispose people to poor or good health. This idea can be traced back to the writings of ancient scholars such as Hippocrates and Galen who proposed that individual differences in the four humours could predict health outcomes. Galen, for example, warned that melancholic women compared with sanguine women had a higher risk for breast cancer (Van Heck, 1997).

This chapter addresses one of the most serious matters in the study of personality disorder that is in danger of permanently handicapping understanding and treatment. It could, in the end, sabotage research and keep the subject as an esoteric one where only a small number of zealots communicate amongst themselves. It is a concern that the two highly respected handbooks recently published on personality disorder (Livesley and Larstone, 2018; Lejuez and Gratz, 2020) have no chapters or discussion sections on the stigma of personality disorders, despite its importance.

Historical chapters in scientific books are generally dull even though they do not intend to be. There is an understandable need to record what happened in the past even though it may be quite irrelevant to what is going on today. We are frequently asked to remember George Santayana’s comment, made by many others, that ‘those who cannot remember the past are condemned to repeat it’ (Santayana, 1905). But this is hardly relevant for a textbook on The Wheel. Those who concentrate on wheel technology are not going to be particularly interested, except in a voyeuristic sense, in how Neolithic people might have been able to move large blocks of stone to Stonehenge for hundreds of miles using primitive garden rollers. But with personality disorder it is different. Without some knowledge of the history of personality disorder current descriptions cannot be placed in any sort of context.

As we have already noted from the history of personality disorder, when very little was known apart from the humoral theory of disease, it was common to think of temperament (aka personality) as the main progenitor of illness, with all other psychological symptoms considered as secondary epiphenomena. For example, Robert Burton described dozens of symptoms linked to the melancholic temperament, rather too many in his view: ‘The tower of Babel never yielded such confusion of tongues as the chaos of melancholy doth variety of symptoms,’ (Burton, 1621; republished 1927).

The term ‘personality difficulty’ will be unfamiliar to most people except as a general concept, but it will be part of the ICD-11 diagnostic spectrum of personality disorder in January 2022. We know a fair deal about it, but it is not a diagnosis. It is listed in the section of the ICD-11 classification for ‘non-disease entities that constitute factors, influencing health status and encounters with health services, that may be of clinical importance’, called Q Factors. The important section for personality difficulty is QE50 (problems associated with relationships). The full QE50 list is shown in Table 3.1.

The two main reasons, we suspect, why most health professionals shy away from assessing personality status is that it is considered both too complicated and too risky. The risky aspect is discussed in Chapter 9 in dealing with stigma. In this chapter, the process of assessment is taken in stages in a form that everybody can appreciate without prior knowledge of the subject. Throughout the book we will be putting the main focus on the new ICD-11 classification of personality disorder, but the general principles of assessment apply to all ways of looking at personality disorder.

How common are personality problems? The honest, if unsatisfactory, answer is: it depends on your definition. Whether most of us have personality problems, or only relatively few of us, is determined by the context in which the problems are measured. In this chapter, we will attempt to be transparent about how personality problems are defined and measured, and the influence this may have on their frequency. But while acknowledging this, there is more consistency in the epidemiology of personality disorder than in many other aspects of the subject.