A condition that went undiagnosed for too long is about to enter the limelight. On Monday the official trailer dropped for the film “Concussion,” starring Will Smith as Dr. Bennet Omalu, the man who identified the brain disease associated with depression and dementia in former professional athletes. Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative disease of the brain found in people with a history of repetitive brain trauma, according to Boston University’s CTE Center. This type of brain degeneration can occur weeks or years after trauma and is associated with memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia. CTE has been known to affect boxers since the 1920s, but only as recently as 2002 was it discovered that the disease affects retired professional football players and other athletes with a history of brain trauma. Omalu, a forensic neuropathologist, identified the condition after examining the brain of deceased Pittsburgh Steeler Mike Webster. Webster lived with severe depression and dementia before he died of a heart attack at the age of 50, The New York Times reported. Upon examining Webster’s brain during an autopsy, Omalu discovered brown and red splotches which turned out to be large accumulations of proteins that affected cells in regions responsible for mood and emotions, GQ reported. He named the disease CTE and published his findings in the July 2005 edition of “Neurosurgery.” The National Football League denied his discovery and requested the article be retracted. The publication did not comply with the request. Smith as Omalu in “Concussion” Next, Omalu examined the brain of former Pittsburg Steelers guard Terry Long, who, after living with depression, took his own life at the age of 45 by drinking antifreeze. Omalu again found evidence of CTE. In 2006, when he examined the brain of Andre Waters, a safety for the Philadelphia Eagles, he again found CTE. Waters, 44, had shot himself after living with chronic pain and severe depression for many years and being denied disability by the NFL, GQ reported. It became clear to Omalu and his colleagues that CTE could be the explanation behind the high rates of depression, dementia and suicide in former NFL players. Despite difficulties in obtaining brains to examine, and suppressive efforts by the NFL, Omalu continued in his research. “You kind of can’t stop because of the importance of the findings,” Omalu’s colleague, Christopher Nowinski, told The Washington Post. “To not keep going would hurt a lot of people.” In 2014, the Department of Veterans Affairs’ brain repository in Bedford, Massachusetts, found evidence of the degenerative brain disease in 76 of the 79 former players it had examined, PBS News reported. Omalu’s work has helped bring about some reform in how the NFL treats concussions and mental illnesses. After a hearing before the House Judiciary Committee in October 2009, for the first time, the NFL publicly acknowledged the existence of long-term effects from concussions, The New York Times reported. Since then the league has shifted away from a denial of the problem and towards concussion management — there are more medical precautions in place for players and the NFL has also donated funds for concussion research. Now that discussion around CTE has become more prevalant, it’s given athletes a chance to speak out. Recently, several former players talked with Jim Trotter of ESPN.com about their post-playing-career battles with depression. See some of ESPN’s coverage on depression in former NFL players below: “It’d be easier to start with which ones do not have depression,” former Green Bay Packers offensive lineman Aaron Taylor told Trotter, according to Bleacher Report. “Observationally, it’s a significant percentage. It varies by degree, obviously, but everyone struggles.” Omalu’s work in discovery of CTE, as well as his advocacy on behalf of professional sports players, will be brought to light in the film “Concussion,” which will be in theaters this December. The recently released trailer shows Smith, who plays Omalu, as he makes his discovery and attempts to educate players, parents and coaches about the dangers of “gridiron dementia,” as CTE is sometimes called — all the while facing obstacles in the form of the NFL and America’s refusal to acknowledge the dangers present in its favorite sport. Watch the full trailer above, and go here for PBS’s timeline of the NFL’s concussion crisis. If you or someone you know needs help, please visit the National Suicide Prevention Lifeline. You can also reach the Crisis Text Line by texting “START” to 741-741. Head here for a list of crisis centers around the world.