Former Dallas Cowboys defensive end Marshawn Kneeland was diagnosed with Stage 1 chronic traumatic encephalopathy (CTE) following his death, according to an analysis of his brain tissue by the Boston University CTE Center. Kneeland died by suicide in November 2025 at the age of 24.
The diagnosis was released by his family through the Concussion & CTE Foundation. "While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing," the family stated. "We share this information to help people understand what NFL and other high contact sport athletes might be struggling with."
Dr. Ann McKee, director of the Boston University CTE Center, noted that CTE has been found in nearly half of the athletes studied who died before age 30. "Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland, because we have found this progressive brain disease in nearly half of the athletes we’ve studied who have died before the age of 30," McKee said.
Dr. Chris Nowinski, CEO of the Concussion & CTE Foundation, commented on Kneeland's diagnosis occurring despite playing in an era with established concussion protocols and improved helmet technology. "Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE," Nowinski said. "Concussion protocols do not prevent CTE, because CTE is caused by repeated head impacts, not just concussions. If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game."
Kneeland began playing tackle football at age 7. He played collegiately at Western Michigan University before being selected by the Cowboys in the second round of the 2024 NFL Draft. In 18 career games, he recorded 26 tackles and one sack. His death occurred shortly after he scored his first NFL touchdown by recovering a blocked punt in the end zone during a game against the Arizona Cardinals.