Dallas Cowboys player's death highlights CTE dangers in contact sports

Researchers at Boston University have confirmed that Dallas Cowboys defensive lineman Marshawn Kneeland was suffering from chronic traumatic encephalopathy (CTE) at the time of his death by suicide in November 2025, aged 24. A postmortem brain tissue analysis revealed stage 1 CTE, the mildest of four stages of the progressive brain disease caused by repeated head impacts.

Dr Ann McKee, director of Boston University's CTE Centre, said the finding was unfortunately unsurprising. "We have found this progressive brain disease in nearly half of the athletes we've studied who have died before the age of 30," she noted. Stage 1 CTE typically presents with headaches, loss of concentration, short-term memory problems, depression and aggressive tendencies.

Kneeland, drafted by the Cowboys in 2024, began playing tackle football at age 7 and played college football at Western Michigan University before joining the NFL. His family released a statement emphasising the importance of understanding what athletes in high-contact sports may face mentally and physically.

What is CTE? Chronic traumatic encephalopathy is a degenerative brain condition linked to repeated head trauma. In later stages, it can trigger mood swings, suicidal ideation, severe cognitive decline and dementia. CTE can only be diagnosed after death.

Experts stress that whilst Kneeland played under modern concussion protocols and improved helmet technology, he still developed the disease. Dr Chris Nowinski of the Concussion & CTE Foundation warned: "We have no reason to believe the current generation is at a lower risk of CTE than previous generations." Boston University researchers caution that whilst CTE contributes to broader health struggles, the causes of suicide remain complex.