Patients with PTSD have neurobiological dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis function. High corticotrophin releasing hormone (CRH) levels and decreased hippocampal volume are major features of the disorder. The mechanisms responsible for these alterations are not known. This study will evaluate the function of cortisol receptors to determine their roles in maintaining PTSD HPA axis dysregulation. Three groups of subjects will take part in the study: Patients with PTSD, healthy control subjects who were exposed to trauma in the past and remained healthy and healthy control subjects who were never traumatized