ABSTRACT
The introduction of the classification of PTSD as a psychiatric disorder in 1980 has been followed by a dramatic increase in research into the biological underpinning of the disorder. This chapter begins with a brief review of the incidence of PTSD in the general population. The epidemiological findings challenge the early assumption that PTSD was a normal response to exposure to a traumatic event and suggest that PTSD is caused by a number of factors which include the pre-existing mental health and background of the individual, as well as the nature of the traumatic experience. The chapter then looks at recent research into the biological responses to trauma. While it is likely that the initial response to a traumatic event will be similar to that experienced in ‘normal stress’, there is mounting evidence that the hypothalamic-pituitary-adrenal (HPA) pathway behaves very differently in people with PTSD. This finding supports the idea that some people may have developed a predisposition for developing PTSD due to an earlier exposure to a traumatic event or other risk factor. Finally, the chapter looks at the brain and the structures most closely related to the trauma experience. Once again, traumatic stress is shown to be different to normal stress in the way it impacts on the functioning of the brain. The formation of an integration barrier blocks any processing of highly distressing trauma sensations and shuts down the language areas in the cortex. This prevents the trauma victim understanding or giving meaning to their experience as being particularly significant.
