The NFL will distribute a new poster to teams that warns of the dangers of concussions in much harsher language than before.
Traumatic brain injury "may lead to problems with memory and communication, personality changes, as well as depression and the early onset of dementia," the document reads.
"Concussions and conditions resulting from repeated brain injury can change your life and your family's life forever."
The acknowledgment of such risks is a significant change from a pamphlet previously distributed to players, starting in 2007.
That pamphlet said: "Current research with professional athletes has not shown that having more than one or two concussions leads to permanent problems if each injury is managed properly."
The new wording was first reported by The New York Times.
NFL spokesman Greg Aiello confirmed the changed language Tuesday.
Aiello said the document was a joint effort of the NFL's and union's medical committees "and reflects their views after wide-ranging consultation with leading medical experts," including the U.S. Centers for Disease Control and Prevention.
"It is intended to present the most current and objective medical information on concussion and will be distributed to the players and clubs in the near future," Aiello said.