Appropriate planning before doing a dangerous sport would somehow make the game less dangerous. calculating the possible results of the sport would give a leverage to the players on what would they expect. thinking also about the possible problems the players might meet while doing the sport would give them an idea on how to overcome them.
Bipolar disorder or manic depression
because it can still cause harm or wrecks even though they are prescribed with it.
Football is a dangerous sport, there are often head collisions which could lead to brain tumors or worse.
A well-known alternative is flag football, if we as a society officialised this to be the official NFL version of football, fewer deaths (or lesser than that) could occur. :)
