The Associated Press reported that Seau's brain was analyzed by a number of experts "in a blind fashion," meaning the experts analyzed several brains without knowing beforehand which one was Seau's.
"I was not surprised after learning a little about CTE that he had it," Seau's son, Tyler, told the Associated Press. "He did play so many years at that level. I was more just kind of angry I didn't do something more and have the awareness to help him more, and now it is too late."
Along with Seau, former Chicago Bears player Dave Duerson and Penn football player Owen Thomas have recently died of suicides connected with chronic traumatic encephalopathy. The Associated Press reports that there are "several dozen" cases of football players with this type of brain injury; NFL player Jacob Bell even gave up his football career because he feared developing the condition, CBS News reported. A recent study also showed that NFL players may face a higher risk of the brain conditions of Alzheimer's disease and amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease) than the rest of the population.
The condition is also of increased risk to people in the military who've suffered traumatic brain injuries, HuffPost's David Wood previously reported.
People with chronic traumatic encephalopathy have experienced repeated brain traumas and concussions, according to the Boston University Center for the Study of Traumatic Encephalopathy. Boxers had been known to be affected by this condition at higher degrees than other people for around a century now, but more research and reports are coming out today about other groups who are at risk.
The condition occurs when the brain tissue begins to degenerate and a protein called tau starts to build up in the brain, the BU Center for the Study of Traumatic Encephalopathy reported. However, this tissue deterioration and protein buildup occur gradually and can occur long after a person has stopped receiving the repeated brain trauma (up to years or decades later).
Just last month, a study published in the journal Brain showed that chronic traumatic encephalopathy -- which is marked by depression, aggression, anger, paranoia and can even lead to dementia -- could be the result of repeated head trauma, like that from football, Reuters reported. That study included 85 brains of people who formerly were athletes or soldiers.
The study showed that CTE typically occurs in four stages, Reuters reported:
Symptoms of stage one CTE include headache and loss of attention. Stage two sufferers may face depression, outbursts of anger and short-term memory loss. Those in stage three encounter executive dysfunction and cognitive impairment. Symptoms of the most severe fourth stage include dementia, aggression and difficulty finding words.
Right now, CTE is only definitively diagnosed after a person has died, Brainline.org reported. Therefore, most of the focus in terms of stopping CTE has rested in prevention versus treatment -- including finding safer ways to play sports that may put athletes at risk of concussions.