San Diego Chargers' Junior Seau rests on the sideline after...

San Diego Chargers' Junior Seau rests on the sideline after injuring a hamstring during the second against the Pittsburgh Steelers in Pittsburgh. (Oct. 1, 1995) Credit: AP

Former All-Pro linebacker Junior Seau, who committed suicide in May two years after finishing an NFL career that lasted two decades, suffered from chronic brain damage, a study by the National Institutes of Health has concluded.

The NIH conducted the study at the request of Seau's family. Seau, who was a member of the Chargers, Dolphins and Patriots, played for 20 seasons before retiring in 2009.

Dr. Russell Lonser, who heads the NFL's research subcommittee on head, neck and spine issues, said in an interview with Newsday that Seau's brain showed evidence of chronic traumatic encephalopathy, a neurodegenerative disease that can lead to dementia, memory loss and depression.

Seau shot himself in the chest May 2, and his family donated his brain to the NIH to have it tested. Lonser said researchers were given the brains of three unidentified people to maintain the integrity of the research, and examinations of all three concluded that Seau had the disease.

"Obviously, with the publicity surrounding Seau's death, if we had just one brain that arrived and the media already reported that his brain was donated to the NIH, it might have caused some issues. So that's why we did it in a way that they were not told," Lonser said.

Lonser, now the chairman of the department of neurological surgery at Ohio State University after recently leaving the NIH, is an unpaid consultant for the league. He said the league, which has donated $30 million to the Bethesda, Md.-based research facility, had no part in the study.

Lonser said it was too soon to draw any sweeping conclusions about whether all football players will eventually suffer from CTE.

"That will only be determined ultimately by a long-term study," Lonser said. "Millions of individuals play football, and it's not just football we're talking about. We're talking also about soldiers who are potentially vulnerable to traumatic insults. There's a whole host of people, not only in football but in other sports, who can be impacted."

The NFL said in a statement Thursday that the finding "underscores the recognized need for additional research to accelerate a fuller understanding of CTE. The NFL, both directly and in partnership with the NIH, Centers for Disease Control [and Prevention] and other leading organizations, is committed to supporting a wide range of independent medical and scientific research that will both address CTE and promote the long-term health and safety of athletes at all levels."

Seau joins a list of several dozen football players who had CTE. Boston University's center for study of the disease reported last month that 34 former pro players and nine who played only college football suffered from CTE.

Seau is the latest NFL player to have killed himself and then found to have CTE. Former Bears and Giants safety Dave Duerson and former Falcons safety Ray Easterling also committed suicide. Studies of their brains found evidence of CTE.

"I was not surprised after learning a little about CTE that he had it," Seau's 23-year-old son Tyler said in an interview on ESPN. "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.

"I don't think any of us were aware of the side effects that could be going on with head trauma until he passed away. We didn't know his behavior was from head trauma."

His ex-wife, Gina Seau, and Tyler Seau said he experienced wild mood swings, irrationality, forgetfulness, insomnia and depression.

"He emotionally detached himself and would kind of 'go away' for a little bit," Tyler Seau said. "And then the depression and things like that. It started to progressively get worse."

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