Human beings have developed over the millennia by adapting successfully to their changing environments. We learn from experience. Through our senses, we constantly monitor and interact with our physical and social environments. Over the generations, mechanisms that have helped the species survive are coded into us. When we are threatened, we react in largely predictable ways. Such reactions have developed to protect us, but sometimes they can hinder adaptation. Strictly speaking, one should say that ‘when we perceive that we are threatened …’ because it is not only the external, objective nature of a threat that determines our reaction to it, but also the way we interpret the threat – the meaning it has for us, the subjective component.
In the past few years, the great strides in understanding and treating anxiety disorders that were achieved by the applications of learning theory and behaviour therapy (see Field & Davey, chapter 8, this volume), have been complemented and enhanced by similar strides coming from the application of findings from experimental cognitive psychology (see Prins, chapter 2, this volume). Rooted in models coming from information processing theories, these cognitive models have been applied to anxiety disorders in general (Brewin, 1988) and to the study of post-traumatic stress reactions in particular (Brewin, Dalgleish & Joseph, 1996; Joseph, Williams & Yule, 1997). This chapter will examine the role of traumatic events in the development of anxiety disorders, particularly post-traumatic stress disorder (PTSD), differentiating between single acute events and chronic and/or repeated ones.