Posttraumatic Stress Disorder remains one of the most contentious and poorly understood psychiatric disorders. Evolution and Posttraumatic Stress provides a valuable new perspective on its nature and causes. This book is the first to examine PTSD from an evolutionary perspective. Beginning with a review of conventional theories, Chris Cantor provides a clear and succinct overview of the history, clinical features and epidemiology of PTSD before going on to introduce and integrate evolutionary theory. Subjects discussed include: The evolution of human defensive behaviours A clinical perspective of PTSD Defence in overdrive: evolution, PTSD and parsimony This original presentation of PTSD as a defensive strategy describes how the use of evolutionary theory provides a more coherent and successful model for diagnosis, greatly improving understanding of usually mystifying symptoms. It will be of great interest to psychiatrists, psychotherapists, psychologists, and anthropologists.