What Is CTE? Former Cowboys Star Marshawn Kneeland Found to Have Brain Disease After Death By Suicide

Former Dallas Cowboys defensive end Marshawn Kneeland was found to have early-stage chronic traumatic encephalopathy after his death by suicide, raising fresh concern about the hidden toll of repeated head impacts in American football.

Researchers at Boston University's CTE Center diagnosed Kneeland with Stage 1 CTE after examining his brain tissue following his death in November 2025.

The former Cowboys player was 24.

Kneeland died after a police chase in Texas, where authorities said troopers attempted to stop him for a traffic violation. Police said he later crashed his car, fled on foot and was found dead from a self-inflicted gunshot wound. His family said the diagnosis offered 'important context' for some of the struggles he had been facing, while stressing that it should not define the final moments of his life.

'We continue to remember Marshawn with compassion for the person he was,' the family said.

What Is CTE?

CTE, or chronic traumatic encephalopathy, is a progressive brain disease linked to repeated blows to the head. It has been found most often in people exposed to repetitive head impacts, including American football players, boxers, rugby players, hockey players and some military veterans.

Unlike a single concussion, CTE is believed to develop over time from repeated impacts, including smaller hits that may not cause immediate symptoms. The disease is associated with an abnormal build-up of tau protein in the brain, which can damage brain tissue and affect mood, behaviour and thinking. At present, CTE can only be confirmed after death through examination of brain tissue.

What Does Stage 1 CTE Mean?

Stage 1 is the mildest of the four recognised stages of CTE.

Common symptoms in the earliest stage can include headaches and problems with attention or concentration. Some people may also experience short-term memory problems, depression, impulsive behaviour or difficulty with planning and decision-making.

In later stages, symptoms can become more severe. Mood swings, aggression, cognitive decline, movement problems and dementia-like symptoms may appear as the disease progresses.

Experts warn, however, that symptoms vary widely and CTE should not automatically be treated as the direct cause of a person's death. Boston University has also noted that suicide is complex and that a CTE diagnosis is not known to be a proven risk factor for suicide.

Football Career Began at Seven

Kneeland began playing tackle football when he was seven years old.

He later played at Western Michigan University before the Dallas Cowboys selected him in the second round of the 2024 NFL Draft. He appeared in 18 games for the Cowboys, including four starts, and was seen as a promising young defensive lineman before his death.

Dr Ann McKee, director of Boston University's CTE Center, said she was 'not surprised' to find the disease in Kneeland's brain because researchers have identified CTE in nearly half of the young athletes they have studied who died before age 30.

Family Hopes Diagnosis Raises Awareness

Kneeland's family said they chose to share the findings to help others understand what athletes in the NFL and other high-contact sports may be going through. The diagnosis also adds to wider concerns about whether modern concussion protocols and improved helmets are enough to protect players.

Dr Chris Nowinski, co-founder of the Concussion & CTE Foundation, said Kneeland played in an era of better equipment and formal concussion rules, yet still developed the disease. For researchers, the case underlines the need to reduce repetitive head impacts, especially among young athletes.

For Kneeland's family, it is also a plea for empathy: to remember the person behind the diagnosis, not only the tragedy of how his life ended.