Post-traumatic Stress Disorder (PTSD) happens after you experience or witness something extremely frightening or a life-threatening situation, for example, a car crash.
Most people take time to get over a traumatic event, but for those with PTSD, this can take a lot longer. People experiencing PTSD might feel stuck with memories of trauma. This may mean that they carry on having dreams, flashbacks or upsetting thoughts about what happened.