Borderline personality disorder (BPD) is a disorder diagnosed predominantly in women, which has a strong association with trauma during childhood. In this thesis I explore these features of BPD further, to elucidate how and why female gender and psychological trauma lead individuals to be diagnosed with BPD. This thesis begins with a review of the literature surrounding borderline personality disorder (BPD). This includes a discussion of the history of BPD and the modern construct. I then consider the individual symptoms of BPD, theories surrounding BPD’s aetiology and an exploration of demographic factors associated with BPD diagnosis.

The two primary demographic factors associated with BPD are female gender and experience of developmental trauma. Therefore, in Chapter 2 I review the literature on gender and psychiatry, including BPD, before going on to discuss the literature surrounding developmental trauma and BPD. I also outline several reasons to suspect that BPD might also relate to psychological trauma in adulthood. Chapter 3 provides information as to the general methods used in this thesis. I used two pre-existing databases to conduct my research, and in this chapter I outline how the original researchers obtained this data.

In Chapter 4 I empirically investigate the frequently observed relationship between female gender and BPD diagnosis. I consider the extent to which this relationship is driven by a genuine relationship, differential service use of men and women with BPD symptoms, or diagnostic bias in assessing the symptoms of BPD. My data and analyses suggest that the gender difference in BPD traits is small and that differences in diagnosis rate likely relate to gender invariance of specific BPD symptoms which may be viewed by clinicians as “core” symptoms.

In Chapter 5 I examine the link between developmental interpersonal trauma and development of mental health conditions including BPD. I consider the role of type of trauma, age at traumatisation and trauma severity in predicting myriad mental health outcomes. I conclude that BPD (and most other mental health conditions) are associated with childhood trauma in all its forms, but that sexual abuse involving intercourse is especially damaging.

In Chapter 6 I investigate the controversial hypothesis that interpersonal trauma experienced in adulthood might contribute to BPD symptomology. BPD has historically been conceptualised as a disorder stemming from developmental trauma, but I provide evidence that individuals traumatised in adulthood may have a presentation of (possibly transient) BPD traits.

In the final chapter of this thesis I relate the findings of the previous three chapters to the literature reviewed in Chapters 1 and 2 and discuss the implications of my findings to research and clinical practice. This includes discussion about the nature of psychiatric diagnoses, whether such conditions should be assessed categorically or dimensionally and whether there are indeed “core” symptoms to BPD rather than just 9 symptoms considered with equal weight. I discuss further the possibility that abuse in adulthood might lead an individual to display more traits of BPD and the effect that this finding might have on clinical practice treating adults who present with BPD or BPD-like conditions.