Post-traumatic stress disorder (PTSD), typically results from witnessing or experiencing an extremely distressing or catastrophic event, or series of events. Most people associate PTSD with military or emergency response incidents, but PTSD can occur in any workplace. PTSD is a mental illness that occurs when a someone experiences something extremely frightening, stressful, or overwhelming. Typically, the event is unexpected, and the person feels powerless to influence the outcome. Often the incident resulting in PTSD involves the threat of death or serious injury. Some examples of such incidents include combat, a natural disaster, a car accident, or an assault. PTSD is a mental illness and can be hard to identify and diagnose. Although some people's onset of PTSD may be quick, others may not notice issues for years.