Relevant here too?

Silence on Concussions Raises Risks of Injury - New York Times

I know nothing of American football, but still it is interesting to read from the above article how big of a problem concussion is in the game:

At least 50 high school or younger football players in more than 20 states since 1997 have been killed or have sustained serious head injuries on the field, according to research by The New York Times.

Mind you, they don't explain what a "serious head injury" exactly is. Still:

Anonymous questionnaires that ask specifically about concussions have reported rates among high school football players at about 15 percent each season; when the word concussion is omitted and a description of symptoms is provided instead, close to 50 percent of players say they had one, with 35 percent reporting two or more.

It's interesting to note that, apart from death, other ongoing problems can be caused:

Experts said that for every such case there can be hundreds of victims of postconcussion syndrome, leaving youngsters depressed, irritable and unable to concentrate, and they sometimes miss school for weeks or perform poorly on tests. Ben Mangan of Lewisburg, Ohio, still has mood swings and cognitive problems deriving from at least one major concussion in 2002.

I wonder how seriously concussion is dealt with in official rugby league circles, and whether any famous players with depression believe (or are told) it may have been caused by it.