A:A concussion is a type of traumatic brain injury that is caused by a blow to the head or body, a fall, or another injury that jars or shakes the brain inside the skull. You don't have to pass out (lose consciousness) to have a concussion. Some people will have obvious symptoms of a concussion, such as passing out or forgetting what happened right before the injury, where others won't. With rest, most people fully recover from a concussion, and recovery can take hours or weeks. In rare cases concussions cause more serious problems. Repeated concussions or a severe concussion may require surgery or lead to long-lasting problems with movement, learning, or speech.