Post-traumatic stress disorder (PTSD) is a group of stress reactions that can develop after we witness a traumatic event, such as death, serious injury or sexual violence to ourselves or to others. PTSD can happen after we've been through one traumatic event, or after repeated exposure to trauma. Sometimes, PTSD can develop after hearing details about devastating and traumatic events many times, like the experience of some emergency workers. It's important to seek help to manage PTSD. There are effective treatments for PTSD, and you can feel better.