Seau's family tells a different story. When asked whether Seau had experienced any concussions in his career, his ex-wife, Gina Seau said, "Of course he had," according to the Associated Press. "He always bounced back and kept on playing. He's a warrior. That didn't stop him. I don't know what football player hasn't. It's not ballet. It's part of the game."
CTE has similar brain features to that of Alzheimer's, Parkinson's and Lou Gehrig's disease.
The Boston University Center has studied more than 75 brains of dead athletes, and has found CTE in more than 50 of them, according to a January Boston Globe article. CTE was originally researched in 1928 in "punch drunk" boxers, or boxers who suffered from dementia because of continuous blows to the head.
Seau is remembered for his gregarious and positive nature, along with his charity work and involvement in the community. But, that's not to say the 12-time former Pro Bowl player didn't have his share of problems.
In October 2010, Seau was arrested after his live-in girlfriend accused him of domestic violence.
Five hours after posting bail and getting released from jail, he drove his car off the side of a San Diego cliff. He walked away from the accident unscathed, but the police initially investigated the accident as a suicide attempt.
"Exactly how the brain damage causes mood disturbance is not clear," said Dr. John Whyte, director of the Moss Rehabilitation Research Institute in Philadelphia, who does not know Seau's medical history. "There could be biological changes going on, or changes in the neurotransmitters that affect mood, or it could be a psychological factor that this brain injury has disrupted work and family life so much that it has really changed your life."
Repeated blows to the head may also damage parts of the brain that have to do with impulse control and the ability to weigh the long-term consequences of decisions.
Nevertheless, until more research has been done, Whyte said, the public should not jump to conclude a definitive link between the hits Seau experienced and his suicide.
"Some people may feel really bad one day, but they can say, 'OK, this thought is out of proportion with reality,'" said Whyte, "whereas, if you're acting on impulse to certain emotions, you may feel bad one day and that can lead you to take action."
While there has been more concern over pro players and suicide in recent years, Whyte said, sports are likely becoming less dangerous because of all the research being devoted to safety guidelines, proper equipment and the aftermath of a career of brain injuries.
In 2009, the NFL instituted new rules that require clearance from independent neurologists to allow players who suffered concussions to return to the field. The league also imposed stricter guidelines to reduce the number of helmet-to-helmet hits.
"The focus on sports safety has become much more vigilant about brain injuries and more strict with return-to-play guidelines," said Whyte. "But we certainly need more research to confirm whether these athletic-related injuries are leading to suicides."