Former Dallas Cowboys DE Marshawn Kneeland diagnosed with stage 1 CTE

Kneeland died by suicide at age 24 during the 2025 NFL season

(Boston) – The family of former Dallas Cowboys defensive end Marshawn Kneeland is releasing the results of his post-mortem brain tissue analysis today through the Concussion & CTE Foundation. Researchers at the Boston University CTE Center diagnosed Kneeland with stage 1 (of 4) chronic traumatic encephalopathy (CTE). Kneeland died by suicide in November 2025 at 24 years old.

“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,” said Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System. “Thanks to the generosity of our brain donor families, we now better understand the earliest stages of CTE, and it is bringing us closer than ever to diagnosing it during life. My team and I are fully dedicated to finding effective treatments and a cure for CTE.”

Kneeland played football at Western Michigan University before being selected by the Dallas Cowboys in the second round of the 2024 NFL Draft. He died during his second NFL season. He started playing tackle football when he was 7 years old.

“Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE,” said Dr. Chris Nowinski, Concussion & CTE Foundation CEO. “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.”

Kneeland’s family, including his girlfriend Catalina Mancera, shared the following statement:

“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. 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.”

Kneeland’s family asks for privacy as they continue to grieve. They will not be doing any interviews at this time.

Suicide is complex and multifactorial. A post-mortem CTE diagnosis should not be considered the cause of a suicide and is not known to be a risk factor for suicide.

The Concussion & CTE Foundation encourages anyone worried about suspected CTE symptoms to reach out to their HelpLine team for medical recommendations and support at ConcussionAndCTE.org/Helpline.

If you or someone you know is struggling, the 988 Suicide & Crisis Lifeline is available 24/7 by calling or texting 988.