Marshawn Kneeland was diagnosed posthumously with stage 1 chronic traumatic encephalopathy after his death in November 2025, adding medical context to the passing of the former Dallas Cowboys defensive end.
Kneeland died on Nov. 6 at 24 years old, and after that, the Collin County Medical Examiner's Office determined he died by suicide. The diagnosis came from researchers at Boston University's CTE Center, where CTE can only be identified after death.
What the diagnosis means
CTE is a progressive brain disease that has been linked to repeated head trauma, and the article notes that symptoms can include memory loss, impulsive behavior and depression. Dr. Ann McKee said she was not surprised to find CTE in Kneeland's brain, noting that the center has found the disease in nearly half of the athletes it has studied who died before the age of 30.
The diagnosis does not change the tragedy of Kneeland's death, his family said, but it does offer important context about some of the struggles he may have been facing. The family also said it shared the information to help people understand what NFL and other high contact sport athletes might be struggling with.
Kneeland began playing tackle football at age seven, a reminder of how early contact can start for players who later reach the NFL. In his second professional season, he was with the Dallas Cowboys, making his diagnosis part of a broader conversation about the long-term toll of football.
His family said it continues to remember him with compassion for the person he was, rather than defining him by the final moments of his life.
