Former NFL running back Larry Johnson, 46, describes symptoms he believes indicate chronic traumatic encephalopathy (CTE), including disorientation and memory lapses. Currently, CTE can only be diagnosed posthumously through brain tissue analysis. Researchers like Michael Alosco of Boston University are developing tests to diagnose CTE in living subjects through the Diagnose CTE Research Project, following over 300 former players since 2015.

A definitive diagnosis could guide treatment and prevent misdiagnosis of treatable conditions, which Harvard researcher Rachel Grashow notes puts players at higher self-harm risk. A 2024 study found nearly one-third of former NFL players with health symptoms believed they had CTE, making them five times more likely to have suicidal thoughts.