Posttraumatic stress disorder is a prevalent mental health problem associated with substantial psychiatric morbidity. Although PTSD had been observed throughout history, PTSD was first introduced in the third edition of the DSM in 1980, and since, there has been a burgeoning amount of literature on this topic. More recently, there has been a rapid expansion in knowledge and interest in understanding risk factors for PTSD and its treatments. Several systematic reviews on the risk factors for development of PTSD have recently been written. In this paper, I will describe the changes in PTSD diagnosis in the DSM, the impact of PTSD in the community, and the most well-established risk and protective factors for PTSD. Throughout the paper, I will highlight clinical implications and controversies.