The severity of brain damage can vary with the type of brain injury. A mild brain injury may be temporary. It causes headaches, confusion, memory problems, and nausea. In a moderate brain injury, symptoms can last longer and be more pronounced. In both cases, most patients make a good recovery, although even in mild brain injury 15% of people will have persistent problems after one year.

With a severe brain injury, the person may suffer life-changing and debilitating problems. He or she will have cognitive, behavioral, and physical disabilities. People who are in a coma or a minimally responsive state may remain dependent on the care of others for the rest of their lives