Researchers have found that former Dallas Cowboys defensive lineman Marshawn Kneeland was living with Stage 1 chronic traumatic encephalopathy (CTE) when he died by suicide in 2025 at the age of 24.

Scientists at Boston University’s CTE Center made the diagnosis after examining his brain tissue following his death. Stage 1 is the earliest form of the disease and is commonly linked to symptoms such as headaches and difficulty with concentration. Researchers also noted that nearly half of the athletes they have studied who died before turning 30 were found to have CTE.

Kneeland’s family said the diagnosis has helped them better understand some of the personal struggles he experienced before his death.

The former NFL player died in November 2025 after a police pursuit in Texas that began with a traffic stop. Authorities said he crashed his vehicle, fled on foot, and was later found dead from a self-inflicted gunshot wound.

Kneeland was selected by the Dallas Cowboys in the second round of the 2024 NFL Draft and played 18 games for the team. He began playing football at the age of seven and later starred at Western Michigan University before reaching the NFL.