Introduced in 1994 as a new diagnoses in the DSM-IV, Acute Stress Disorder (ASD) is caused by exposure to severe trauma, which is defined as a stressor that causes intense fear and, usually, involves threats to life or serious injury to oneself or others. The symptoms of ASD include a combination of one or more dissociative and anxiety symptoms with the avoidance of reminders of the traumatic event. The disorder is transient, and often a precursor to PTSD. Information on Acute Stress Reaction may also be found here.