Researchers said Monday that Chicago Bears star Dave Duerson had developed a disease from brain trauma that has been found in more than 20 deceased former football players. Duerson died via a self-inflicted gunshot wound on Feb. 17. Many people believe that his deteriorating mental state came from brain trauma from his time in the NFL. Duerson shot himself in the chest, writing in his suicide note, “Please see that my brain is given to the NFL’s brain bank.” His death rattled the football community. Despite recent advances by the Center for the Study of Traumatic Encephalopathy at Boston University and other research institutes, the brain trauma incurred by football players remains irreversible.