Dallas Cowboys' Marshawn Kneeland diagnosed with CTE after death by suicide, researchers say
Dallas Cowboys defensive end Marshawn Kneeland was suffering from stage 1 chronic traumatic encephalopathy, or CTE, when he died by suicide last year.
Scientists at the Boston University CTE Center made the diagnosis following post-mortem brain tissue analysis, according to a statement Tuesday from the Concussion & CTE Foundation.
Kneeland, 24, was in the middle of his second season with the Cowboys when Frisco police officers found his body in the early morning hours of Nov. 6, 2025, following a police chase.
CTE is a degenerative brain disease linked to repeated head trauma, including concussions and other hard hits to the head. It can only be diagnosed after death.
"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," Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, said in a statement.
The Concussion & CTE Foundation said that suicide is complex, and the diagnosis should not be considered the cause of a suicide.
In a statement, Kneeland's family said the diagnosis provides "important context" about some of the struggles he may have been facing.
"We share this information to help people understand what NFL and other high-contact sport athletes might be struggling with. Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life. One Love," the statement said.
Kneeland played at Western Michigan University in college and started playing tackle football at 7 years old, the statement said. A 2018 study found that children who play football before age 12 show CTE-related symptoms sooner.
Over the past two decades, the risk of CTE has been at the center of player safety discussions at all levels of tackle football. Another 2018 study found CTE in the brains of 87 deceased NFL players, including Hall of Famer Junior Seau. Since then, other players, including star wide receivers Demaryius Thomas and Vincent Jackson, were both diagnosed, as well.
"Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE," Dr. Chris Nowinski, CEO of the Concussion & CTE Foundation said in a statement. "We have no reason to believe the current generation is at a lower risk of CTE than previous generations. 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."
