Acute stress disorder is diagnosed when a person is experiencing a reaction; severe anxiety, dissociation, and other symptoms to a severe physical or emotional shock that has occurred in the recent past (within the past month).
This disorder is related to PTSD (Post-Traumatic Stress Disorder) but ha much more limited diagnostic time frame. When a person experiences a severe shock such as a car accident the individual may develop dissociative symptoms and may experience a decrease in emotional responsiveness and often find it difficult or impossible to experience pleasure in previously enjoyable activities. They may frequently also feel guilty about pursuing their usual life tasks.