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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. Although there may be cuts or bruises on the head or face, there may be no other visible signs of a brain injury.
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. But other people won't. With rest, most people fully recover from a concussion. Some people recover within a few hours. Other people take a few weeks to recover.
It's important to know that after a concussion the brain is more sensitive to damage. So while you are recovering, be sure to avoid activities that might injure you again.
In rare cases, concussions cause more serious problems. Repeated concussions or a severe concussion may lead to long-lasting problems with movement, learning, or speaking. Because of the small chance of serious problems, it is important to contact a doctor if you or someone you know has symptoms of a concussion.