Acute stress reaction (ASR, also known as psychological shock, mental shock, or simply shock) and acute stress disorder (ASD) is a psychological response to a terrifying, traumatic or surprising experience. Combat stress reaction (CSR) is a similar response to the trauma of war. The reactions may include but are not limited to intrusive or dissociative symptoms, and reactivity symptoms such as avoidance or arousal. It may be exhibited for days or weeks after the traumatic event. If the condition is not correctly addressed, it may develop into post-traumatic stress disorder (PTSD).