Doctors at Boston University determined that former Bears Dave Duerson's brain had "classic" and "moderately advanced" symptoms of Chronic Traumatic Encephalopathy.
CTE is a degenerative brain disease linked to repeated head trauma.
"When you look at the brain microscopically, it's indisputable. There's no evidence of any other disorder," said Dr. Ann McKee, co-director of the Center for the Study of Traumatic Encephalopathy at BU. "He has the classic appearance of [CTE]..."
"He had severe involvement of all the structures that affect things like judgment, inhibition, impulse control, mood and memory," said McKee, who is also director of Neuropathology and Brain Banks for New England VA Medical Centers.
Duerson died at 50, when he shot himself in the chest in February and insisted that his brain be examined by Boston University's Center for the Study of Traumatic Encephalopathy.
Duerson is the 14th of 15 former NFL players studied at the VA CSTE Brain Bank to be diagnosed with CTE.
Duerson, who starred at Notre Dame, played safety in the NFL for 11 seasons, starting with the Bears. He was named to four Pro Bowls and won two Super Bowls.
Duerson's family had requested the findings of his brain be made public. The center now has more than 70 brains of former athletes and military veterans. The NFL provided a $1 million gift to the CSTE.
"My father was a man of many accomplishments, both on the field and off the field. With these accomplishments came many battles," said Duerson's son Tregg. "It is my greatest hope that his death will not be in vain, and through this research, his legacy will live on."
Tregg Duerson urged the greater football community to support CTE research.
Doctors also said that Duerson had 10 known concussions during his NFL career, but they do not know if he had any before that.
UPDATE: The NFL issued a statement.
"We once again express our deepest sympathy to the Duerson family. Dave Duerson was an outstanding player, but an even better person, including being recognized in 1987 as the NFL Man of the Year (now the Walter Payton Award) for his significant contributions to community service. We hope these findings will contribute more to the
understanding of CTE. Our Head, Neck and Spine Medical Committee will study today's findings, and as a league we will continue to support the work of the scientists at the Boston University Center and elsewhere to address this issue in a forthright and effective way. We also will continue to ensure that concussions are properly treated in the NFL,
expand the help we are providing to our retired players, further evaluate playing rule and policy changes to reduce and prevent unnecessary contact with the head, and advocate for the passage of Lystedt laws in all states to better protect young athletes in that
suffer concussions in any sport."