Former NFL running back Larry Johnson said in an interview he believes he suffers from chronic traumatic encephalopathy, a brain disease known as CTE.
CTE, which doctors say can be caused by repeated blows to the head, only can be diagnosed after death.
The 38-year-old Johnson, who last played in the NFL in 2011, told the Washington Post he is convinced he is living with CTE as he battles self-destructive impulses in what he calls "the demons."
Johnson described multiple symptoms of anxiety, paranoia, intense headaches, the jitters, mood swings, violence and forgetfulness, which he calls "Blank spots."
"If I can't remember who I was, I've got YouTube; I've got music videos that I'm making for myself, so when I watch these things I can remember," Johnson told the Washington Post. "I'm trying to get these things in order so she knows who I am and what I came from."
Johnson described an incident when those demons pushed him toward the barrier of a rooftop deck of an apartment building, urging him to "jump."
"One is telling you to do it; one is telling you don't," Johnson, a two-time Pro Bowler in 2005 and 2006 with the Kansas City Chiefs, told the newspaper. "One is telling you it'd be fun."
"A bittersweet thing: I'm going to be free of everything that's holding me down," Johnson said. "The same way Aaron thought: I'm going to be gone from this world, but I'm still going to be able to take care of my child, because that's all I care about."
Johnson has a history of violence off the field -- he has been arrested six times, five of which were for various assault charges against women.
Johnson, who played at Penn State and was a Heisman finalist in 2002, was drafted No. 27 overall in 2003 by the Chiefs and played nine seasons in the NFL. He also spent time with the Cincinnati Bengals, the Washington Redskins and the Miami Dolphins, finishing his career with 6,223 rushing yards and 55 touchdowns.