Late Cowboys defensive end Marshawn Kneeland diagnosed with CTE

Former Dallas Cowboys defensive end Marshawn Kneeland has been posthumously diagnosed with Stage 1 chronic traumatic encephalopathy (CTE). Kneeland died by suicide in November 2025. He was 24.

Boston University's CTE Center announced the diagnosis following Kneeland's family donating his brain for research. According to the center, there are four stages of CTE, and Stage 4 has the most damage.

The Concussion & CTE Foundation shared the news on social media on Tuesday.

"Former Dallas Cowboys DE Marshawn Kneeland has been diagnosed with stage 1 CTE by (Boston University CTE Center) researchers after his death during the 2025 NFL season at age 24," the post stated.

Kneeland's family, including his girlfriend, Catalina Mancera, also released a statement, per ESPN.

Former Dallas Cowboys defensive end Marshawn Kneeland's family releases 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," the statement from his family and girlfriend reads. "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 BU CTE Center also released a comment stating that suicide is "complex and multifactorial" and that a "post-mortem CTE diagnosis should not be considered the cause of a suicide."

The Concussion & CTE Foundation adds that "if you or a loved one are worried about suspected CTE symptoms, reach out to our HelpLine team for doctor recommendations, education, and support" at their official website.

If you are in the United States and you or a loved one have contemplated suicide, call the National Suicide and Crisis Lifeline at 988 or 1-800-273-TALK (8255) to connect with a trained counselor.