NFL great Junior Seau had a degenerative brain disease when he committed suicide last May, the National Institutes of Health told The Associated Press on Thursday.

Results of an NIH study of Seau's brain revealed abnormalities consistent with chronic traumatic encephalopathy (CTE).

The NIH conducted a study of three unidentified brains, one of which was Seau's. It said the findings were similar to autopsies of people "with exposure to repetitive head injury."

Seau was an outstanding linebacker for 20 NFL seasons before retiring in 2009. He died of a self-inflicted shotgun wound.

Seau joins a list of several dozen American 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.