Marshawn Kneeland Diagnosed with CTE After Death

Former Dallas Cowboys defensive end Marshawn Kneeland was posthumously diagnosed with Stage 1 chronic traumatic encephalopathy. He died by suicide on November 6, 2025 at the age of 24, just two seasons into his professional career. The Boston University CTE Center identified the brain disease in his tissue, adding his name to a growing list of young athletes affected. Dr. Ann McKee, the center’s director, said the finding was “unfortunately” expected given the pattern among athletes who died before 30.

What Is CTE?

CTE is a degenerative condition that destroys nerve cells after repeated head impacts. It can only be confirmed after death through brain examination, making early detection difficult. The disease is most common among players in high‑contact sports, military personnel, and first responders. BU’s research shows nearly all young athletes studied had mild (Stage 1) CTE, with symptoms ranging from memory loss to depression.

The stages run from one to four, with Stage 4 being the most severe. Affected individuals may suffer from impaired judgment, aggression, and even suicidal tendencies. Over the past few years, the Boston center has documented cases across multiple levels of sport.

Rising CTE Diagnoses Among Former Players

A 2024 Mass General Brigham study of roughly 2,000 former NFL athletes found about one‑third believe they have CTE. In a separate BU analysis of 376 former players, 91.7 percent were diagnosed posthumously. The Canton brothers, John and Ed Grimsley, are among the high‑profile names now linked to the condition. Those figures illustrate how widespread the issue has become.

Career length appears to amplify risk, with players who logged five or more seasons facing double the chance of neurodegenerative death. The overall mortality rate for NFL veterans is actually lower than the general population, but the disparity grows when focusing on diseases like dementia and Parkinson’s. These statistics underline the need for better safety protocols throughout a player’s career.

Notable Cases of CTE in Former Football Players

Historical diagnoses include Jim Houston, a Browns linebacker, and Conrad Dobler, an offensive lineman for the St. Louis Cardinals. Junior Seau, the San Diego Chargers linebacker, and Mark Tuerk, a Washington offensive lineman, also received postmortem CTE findings. Each case adds to the evidence that the disease affects players at every position and era.

Research from Boston University and Mass General Brigham continues to uncover new insights into the long‑term impacts of repeated head trauma. The data suggest that prevention and early mental‑health support must become integral parts of the sport’s culture.

As more cases emerge, the conversation shifts from awareness to action. Teams, governing bodies, and medical professionals are pressured to adopt stricter concussion guidelines and improve player monitoring. The fate of athletes like Marshawn Kneeland highlights the urgent need for systemic change to protect future generations.