High Quality Content by WIKIPEDIA articles! Concussions, a type of traumatic brain injury, have been a notorious issue in sports, being a notable reason for player suicides and retirements due to chronic traumatic encephalopathy (CTE) from their playing careers. Over 1.6 million Americans have sustained concussion-related injuries, a number that has since then grown in high school and college athletes. Because of the fact that concussions cannot be seen on X-rays nor CT scans, attempts to prevent concussions have been difficult. As of 2012, the four major professional sports leagues in the United States and Canada have concussion policies.