The role of dissociation in the development and maintenance of post-traumatic stress disorder
The aim of this thesis was to investigate psychological factors influencing the development and maintenance of post-traumatic symptoms, with particular attention to the role of dissociation. The concept of dissociation is at present not well understood, and a secondary aim of this thesis was to clarify its meaning and structure and enable its assessment. Chapter 2 reports the development and testing of a questionnaire measuring trait dissociation, and the factor analysis of this questionnaire into seven sub-factors with low to medium intercorrelations, along with an analysis of the reliability and validity of this questionnaire, which was used in the subsequent studies. Chapters 3 and 4 consist of experimental studies investigating the relationship between dissociation and later intrusive memories using a videotape of scenes from road traffic accidents as a stimulus. The first study attempted to manipulate dissociation, while the second used extreme scorers on the trait dissociation questionnaire. The manipulation of dissociation proved difficult, but both studies showed a relationship between dissociation and later intrusions. Chapters 6 and 7 report on two prospective clinical studies following road traffic accident victims over the first six months following their accident, and investigates the role of dissociation and other psychological factors in the development of post-traumatic symptoms. Both state and trait dissociation, and the emotional numbing subfactor of dissociation in particular, predict the later development and maintenance of other post-traumatic symptoms. Persistent dissociation was more predictive of later symptoms than dissociation in the first few days after the accident. These results are discussed in relation to current thinking about the concept of dissociation and the DSM diagnoses of post-traumatic stress disorder and acute stress disorder. In particular it seems useful to distinguish between components of dissociation in terms of their relationship to PTSD. Possible future research and clinical implications are also addressed.