NFL defensive lineman Marshawn Kneeland was found to havestage 1 chronic traumatic encephalopathy (CTE) at the time of his suicide last year, according to researchers.

Experts from Boston University's CTE Center reached this conclusion after examining brain tissue from the Dallas Cowboys player, who passed away at age 24.

"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 the centre's director, Dr Ann McKee.

Stage 1 represents the mildest form of CTE's four stages, where headaches along with reduced attention or concentration often appear.

Kneeland's family issued a statement noting that the diagnosis offered "important context" regarding challenges he encountered.

"We share this information to help people understand what NFL and other high-contact sport athletes might be struggling with," they said.

"We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life."

Kneeland died in November 2025 following a pursuit by Texas State Troopers who attempted to stop him for a traffic issue. Authorities reported that he lost control of his vehicle, fled on foot, and was discovered deceased from a self-inflicted gunshot wound early the next morning.

The Cowboys selected Kneeland in the second round of the 2024 draft. He appeared in 18 games for the team, with four starts. He began playing tackle football at age seven and competed for Western Michigan University prior to joining Dallas as a defensive end.

Studies indicate that participants in American football, rugby, and combat sports face notably elevated chances of developing CTE compared to the broader population.

CTE diagnosis is possible only after death. The condition, triggered by repeated head blows, has appeared in the brains of hundreds of ex-NFL players.

The Boston University CTE Center reported in 2023 that it had identified CTE in 345 of the 376 former NFL players examined.

The NFL reached a $1bn (£700m) settlement following a lawsuit from over 5,000 retired players. More than 21,000 former players may qualify for payments.

During the initial stage of the disease, individuals may also face short-term memory difficulties, depression, aggressive behavior, and problems with executive function, per the CTE Society.

These issues intensify in later stages, with additional symptoms such as mood swings and suicidal ideation potentially arising.

In the most advanced stage, severe cognitive impairment, memory loss, and dementia can occur, according to the CTE Society.

Boston University's CTE Center noted that suicide causes are multifaceted and that a CTE diagnosis is not established as a direct risk factor for suicide.

Nevertheless, CTE researchers emphasized that insufficient measures have been taken to reduce disease risk among athletes.

"Mr Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE," said Dr Chris Nowinski, co-founder and CEO of the Concussion and CTE Foundation.

"We have no reason to believe the current generation is at a lower risk of CTE than previous generations."