Mitchell said that friends of Seau's who were at his charity golf tournament a month ago said his ''spirits were great.''
Boston University's Center for the Study of Traumatic Encephalopathy has analyzed the brains of dozens of former athletes, including that of former Chicago player Dave Duerson, who shot himself in the chest last year.
While saying it was saddened by Seau's death, center officials would not say if they have reached out to the Seau family or would be interested in studying his brain.
Duerson's family has filed a wrongful death suit against the NFL, claiming the league didn't do enough to prevent or treat concussions that severely damaged Duerson's brain before he died in February 2011.
Former Atlanta Falcons safety Ray Easterling, who had joined in a concussion-related lawsuit against the league -- one of dozens filed in the past year -- shot himself last month at age 62. His wife has said he suffered from depression and dementia after taking years of hits.