Two out of five of the authors of an influential medical article on concussions among professional football players say that their co-authors added a conclusion, without their knowledge, that “it might be safe” for high-school and college players to return to games in which they had suffered the brain-joggling injuries, The New York Times reported on Sunday.

The paper, commissioned by the National Football League and published in the journal Neurosurgery in 2005, recommended that doctors for high-school and college athletes “keep an open mind” about the issue, and it has influenced the care of those players ever since. One of the two critical authors said the conclusion had been added at a final stage of proof, when authors do not expect to find their colleagues making major changes.

The paper’s two lead authors said they had added the controversial conclusion — at the behest of peer reviewers who sought to broaden the article’s scope beyond professional players, they said — and stood by their findings. They also said they were not to blame if their findings, intended only to “stimulate interest,” were misinterpreted as guidelines.

An article published today in The Chronicle describes a recent rise in the number of concussions in college sports, particularly among female athletes, in what one university’s athletics trainer called “a hidden epidemic.” —Andrew Mytelka