Posttraumatic Stress Disorder (PTSD) is a common chronic anxiety disorder that is often debilitating and follows exposure to an overwhelming traumatic event. The burden of PTSD on individuals and society is significant. The majority of PTSD sufferers also meet the diagnostic criteria for several other psychiatric disorders and many attempt suicide. Despite the devastating impact of PTSD on the lives of millions worldwide, little is known about the etiology or pathophysiology of this disorder. Although disruptions in the hypothalamic-pituitary adrenal (HPA) Axis, noradrenergic, serotonergic systems have been proposed as neurobiological substrates in the development of PTSD, the exact underpinnings of the neurobiology of PTSD remain to be fully elucidated.