Marshawn Kneeland had early stage CTE when he died at 24

Former Dallas Cowboys defensive end Marshawn Kneeland died by suicide in November 2025 after a high-speed chase with police, and was found to have early stage chronic traumatic encephalopathy (CTE), a brain condition associated with repeated concussions. His family announced this information on Tuesday, revealing that researchers from the Boston University CTE Center conducted an analysis of Kneeland’s brain tissue posthumously. They determined that Kneeland, who was 24 at the time of his death, was in stage one of four of CTE, a degenerative disease commonly found in athletes involved in contact sports, combat veterans, and individuals who suffer from repetitive head trauma. CTE has been known to cause symptoms such as violent mood swings, impulsive behavior, and depression, and it can only be diagnosed after death.

Kneeland’s family, including his girlfriend, Catalina Mancera, expressed in a statement through the Concussion and CTE Foundation how this diagnosis adds context to the struggles he may have faced. They emphasized the importance of understanding what athletes in the NFL and other high-contact sports deal with. "Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was," they said.

The diagnosis has also been linked to the deaths of other NFL players, as well as athletes in hockey and soccer. Kneeland’s tragic end followed an incident in which he evaded police after failing to stop for a traffic violation and subsequently crashed his vehicle. Authorities lost track of him until they found the car wrecked, but while searching for him after he fled on foot, a dispatch reported that Kneeland had sent a group text saying goodbye, suggesting suicidal intentions.

A study by Harvard Medical School and the Boston University CTE Center noted that NFL players are more than four times as likely to develop ALS compared to the general male population. Dr. Chris Nowinski, CEO of the Concussion + CTE Foundation, remarked on Kneeland’s diagnosis amid contemporary concussion protocols in sports, clarifying that these protocols do not prevent CTE, which results from repeated head impacts. Kneeland began playing football at the age of seven and played at Western Michigan University before being drafted by the Cowboys in the second round of the 2024 NFL draft.

Dr. Nowinski stated, "If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game."