On Tuesday, the American Medical Association published its findings of the largest study of its kind into the link between football and CTE, the degenerative brain disease thought to be responsible for memory loss, bouts of uncontrollable anger and violence, and severe depression or suicide.
CTE, or chronic traumatic encephalopathy, can only be diagnosed posthumously. More than 200 brains from deceased football players were donated for the study, including 111 from former NFL players. Of the 202 brains examined, 177 of them—or 88 percent—were diagnosed with CTE. Among the 111 NFL players examined, all but one of them exhibited the disease.
Because the study relies on self-selecting donors rather than a random sample, the results are likely somewhat skewed. A family might be more willing to donate a relative’s brain to the study if he displayed symptoms, for instance.
The problem isn’t contained to the highest, most physical levels of the game, though. Dozens of youth football players have died playing the game in recent years, and according to the AMA study, three of the 14 high school players and 48 of the 53 college players examined had the disease.
For years, the NFL refused to acknowledge any connection between their sport and the degenerative brain disease. But a growing body of evidence—coupled with an increased aversion to the sport amongst concerned parents—led the league to finally admit a correlation and begin taking more proactive measures to improve safety. In 2015, the league settled a multi-billion dollar lawsuit brought by thousands of former players who were suffering from various medical conditions associated with traumatic head injuries.
“The NFL is committed to supporting scientific research into CTE and advancing progress in the prevention and treatment of head injuries,” the NFL said in a statement to CNN.
Their commitment wasn’t always so steadfast. Just last year, the NFL threatened to sue the New York Times after the paper published a report alleging the NFL obstructed and obfuscated concussion research by omitting key data.
It’s also unclear what the future of concussion research will look like in the current administration. Donald Trump has been critical of the emphasis being placed on concussion research, calling out football in particular for growing “soft like our country has become soft,” and much of the research into CTE relies on federal funding.