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, the director of Neuropathology Care at BU's Alzeimer's Disease Center. "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."
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.