Seven months after the unexpected death of former Broncos wide receiver Demaryius Thomas, doctors from Boston University have revealed Thomas suffered from Stage 2 chronic traumatic encephalopathy (CTE) late in his life, as The New York Times reported and Thomas' family announced. Doctors previously indicated that Thomas died from a seizure stemming from a 2019 car crash, but the degenerative brain disease contributed to "increasingly erratic" behavior beforehand, Ken Belson reports.

The last year of Thomas' life was "marked by the memory loss, paranoia and isolation that are hallmarks" of CTE, Belson wrote, citing those close to the late wide receiver. Boston University's medical team on Tuesday agreed with previous consensus that Thomas likely died due to complications from his car crash, noting that seizures "attacked with little or no warning and led Thomas to wreck other cars and fall down steps." But the former first-round draft pick, who announced his NFL retirement just months before his death, had family concerned about his well-being even before the seizures began in 2020.

Thomas' family has released the findings of Boston University CTE Center's brain study through the Concussion Legacy Foundation (CLF) to raise awareness of CTE. Stage 2 CTE is associated with progressive behavior, cognitive and mood abnormalities, per CLF. Thomas developed depression, anxiety, panic attacks and memory troubles before his death. 

"He had two different conditions in parallel," Dr. Ann McKee, a neurologist and leading authority on CTE, told The Times. McKee has diagnosed more than 300 former NFL players with CTE and advocates through CLF for the "public at large (to) stop ignoring the risks of American football and insist that the game be changed to reduce subconcussive hits ... (and that) athletes be comprehensively evaluated at the beginning and end of every season."

Katina Smith, Thomas' mother, revealed to The Times that the former Broncos star informed her after retiring that "his peripheral vision was diminished," while his father, Bobby Thomas, said that the receiver's paranoia increased late in life "to the point that he never left home without a gun." Roughly a year before his death, per Belson, Thomas' plans for a potential NFL comeback were put on the backburner amid increasing dependence on medical care, such as anti-seizure medication, ozone therapy and hyperbaric chamber treatment.

Thomas retired as one of the most productive receivers of his time, totaling 9,763 receiving yards in 11 seasons coming out of Georgia Tech. One of Peyton Manning's favorite targets during Denver's 2015 Super Bowl run, he ended his career with more than a dozen franchise receiving records.