The actual scientific article that brought CTE in football to light is "Chronic traumatic encephalopathy in a National Football League player," published in Neurosurgery. 2005 Jul;57(1):128-34. The full author list is: Omalu BI, DeKosky ST, Minster RL, Kamboh MI, Hamilton RL, Wecht CH. An abstract of the article is available at the US National Library of Medicine website (PubMed) and the full article is available from the journal's publishers (for a fee).
In his office, when Dr. Julian Bailes prepares Mike Webster for a Haldol injection by helping him on the sofa, there's a close-up of a mounted cross-section of a bird's skull placed on the table to Mike's right. The skull is a woodpecker's and shows the unique tongue system that functions as a shock absorber for its brain when it pecks at trees. Dr. Omalu explains the mechanism to Dr. Steve DeKosky later in the film. ("It is the anatomical equivalent of a safety belt for its brain.")
Football helmets do have warning stickers and have had them for several decades. Although the text has varied according to manufacturer and time, they usually warn players not to use the helmet to "butt, ram, or spear an opponent" and that "no helmet can prevent all such injuries".
There are several photographs of John F. Kennedy visible in Cyril H. Wecht's office. The real Wecht is known for, among other things, his criticism of the Warren Commission's findings on the Kennedy assassination and Peter Landesman's previous film Parkland (2013) was a decidedly pro-Warren Commission findings telling of the Kennedy assassination.
Although never mentioned in the film Chris Nowinski an American author, co-founder and executive director of the Concussion Legacy Foundation, and a former professional wrestler with World Wrestling Entertainment and renowned for being WWE's first Harvard alumnus, wrote Head Games: Football's Concussion Crisis, which examined the long-term effects of head trauma among athletes. Nowinski played an integral role in the discovery of the fourth case of chronic traumatic encephalopathy (CTE) in a former NFL football player, former Pittsburgh Steelers offensive lineman Justin Strzelczyk, who was killed in a fiery automobile crash in 2004 at age 36 after a 37-mile police chase at speeds up to 100 miles per hour on the wrong side of the highway. Julian Bailes, the chairman of the department of neurosurgery at West Virginia University and the Steelers' team neurosurgeon during Strzelczyk's career, insisted to Nowinski over a phone conversation that he thought Strzelczyk's death, which was precipitated by strange behavior that some had labeled as "bipolar", was worth looking into due to its similarities to the Andre Waters case. Nowinski contacted Omalu, who discovered the brain was still available, and Nowinski called Mary Strzelczyk, Justin's mother, to ask for permission to Omalu to examine it for CTE. Omalu's positive diagnosis was confirmed by two other neuropathologists.
Prior to Mike Webster's death, during the worst of his CTE-related mental issues, this movie shows him alone in his truck (where he has started living) when he removes his pants and applies a Taser-style electronic weapon to his own heavily scarred leg. Although the movie never provides an explanation for this action, articles on ESPN.com and in GQ covering Webster's death and Bennet Omalu's research explained that Webster did this to himself because at that point in his illness he was unable to fall asleep, but the Taser would at least render him unconscious for periods of time.
When Dr. Bennet Omalu and Dr.Cyril H. Wecht are discussing putting warning labels on football helmets, Dr. Wecht's comment about putting the label on both sides of the helmet is a tongue-in-cheek reference to the fact that the local team, the Pittsburgh Steelers, is unique among NFL teams in having their logo on only one side of the helmet (the right side).
Mike Webster died at 50 from a heart attack. His life after football found him living in car, sleeping in train stations and being arrested for forging 19 Ritalin prescriptions. He said that he used the drug to help with his brain damage caused by concussions. Doctors determined that his frontal lobe was damaged causing cognitive dysfunction. At the time of his death he was "homeless, unemployed, deep in debt beset with medical ailments, lacking in health insurance" and in the middle of a divorce.
Dave Duerson's family was upset with the portrayal of his character in the movie. There were two scenes they say never happened. The first is a scene in which Dr. Omalu is stopped by Duerson from entering a medical conference, and is then called a quack (by Duerson) and told to go back to Africa and "get away from our game." The family says it never happened. Another scene that the Duerson family considers manufactured shows a standoff between Duerson and Andre Waters, a former player whose application for benefits was denied by a retiree board that included Duerson. Waters surprises Duerson outside NFL headquarters, where Duerson dismisses his plea. The movie suggests that had Duerson helped Waters, his suicide might have been prevented.
The mentally ill Mike Webster (David Morse) pulls out his teeth and superglues them back in. Coincidentally, David Morse's ex-CIA agent in World War Z also pulls his teeth out, in a bid to make himself ineffective if he were to become a zombie.