Former rugby league player Ian Roberts has predicted the ‘‘end of contact sport’’ after being diagnosed with brain damage he believes is the result of being knocked out up to a dozen times in his playing career.

Roberts, who played for South Sydney, Manly, North Queensland, NSW and Australia during his career, was told he had returned ‘‘abnormal’’ results after agreeing to undergo testing on his brain as part of a study into the effects of concussion on players in Australia’s football codes.

Ian Roberts was one of rugby league's toughest forwards in the 1980s and '90s. Credit:Simon Alekna

‘‘I’ve got brain damage ... that’s the nuts and bolts of it mate,’’ Roberts told Fairfax Media’s Peter FitzSimons during an interview on Channel Seven’s Sunday Night program. However, Roberts said he was not surprised by his test results and revealed he had been suffering depression.

‘‘It’s not comfortable knowing that,’’ Roberts said. ‘‘But I have got to tell you, Fitzy, I came here expecting to hear that.’’