Duerson, 50, had suspected he suffered from a neurodegenerative disease linked to concussions and instructed in his suicide note that his brain be donated to Boston University's Center for the Study of Traumatic Encephalopathy.
Dr. Ann McKee, a BU neurologist, confirmed Monday a postmortem examination revealed Duerson indeed suffered from the condition, the Los Angeles Times reported.
"The pathology was severe in areas of the brain that influence impulse control, inhibition, emotion and memory," she told the newspaper.
Like some other former NFL players, Duerson -- a four-time Pro Bowl selection and a member of the Bears' 1986 Super Bowl championship team -- complained before his death of headaches, memory loss and uncontrollable impulses.
A group of former players maintains the NFL isn't providing adequate pensions and healthcare for ailing veterans.
The league said in a statement to the Times it has pledged to "further evaluate playing rule and policy changes to reduce and prevent unnecessary contact with the head."