Former Denver Broncos wide receiver Demaryius Thomas had stage 2 chronic traumatic encephalopathy, a form of brain degeneration that has been found in other athletes, his family announced Tuesday.
Thomas, 33, was found dead in his Georgia home in December. The Fulton County Medical Examiner's Office said a copy of his autopsy report was not ready for release; authorities have said foul play was not suspected.
Katina Smith, Thomas' mother, said her son started displaying changes, like isolation, before his death.
Stage 2 of the condition, known as CTE, is often linked to progressive behavior, mood and cognitive abnormalities, the Concussion Legacy Foundation said Tuesday in a news release. Thomas suffered from depression, anxiety and panic attacks and had trouble with his memory, the foundation said.
Smith said in a statement: "He was just so young, and it was horrible to see him struggle. His father and I hope all families learn the risks of playing football. We don’t want other parents to have to lose their children like we did."
Dr. Ann McKee, the director of the Boston University CTE Center, said she hopes the news is a wake-up call. The center diagnosed Thomas with CTE after his family agreed to donate his brain.
"The question I keep asking myself is ‘When will enough be enough?’ When will athletes, parents and the public at large stop ignoring the risks of American football and insist that the game be changed to reduce subconcussive hits and that the athletes be comprehensively evaluated at the beginning and end of every season?" McKee said in the statement.
LaTonya Bonseigneur, Thomas' cousin, had said the family believed his death was related to a seizure. She said he had suffered seizures for more than a year before he died.
Thomas’ personal driver found him after a concerned friend asked that someone check on him.
The Concussion Legacy Foundation said that seizures are often associated with late-stage CTE and that it believes Thomas developed post-traumatic epilepsy after a car accident and a fall he experienced several years before he died.
Thomas is among more than 300 former professional players diagnosed with CTE. Little is known about the condition, according to the Mayo Clinic. It can be diagnosed only through an autopsy, because it requires evidence of degeneration of brain tissue.
The NFL has acknowledged that there is a link between CTE and the sport. In recent years it has overhauled its concussion protocols to impose stricter penalties and restrictions on players.