Some of the folks on this thread, insisting football can't possibly have been a factor because They Believe™, willfully ignore the physical brain studies.
I've seen what brain injury can do to a person and can understand why these players would take their lives before they full lost control and became unrecognizable as themselves.
As I said above, the hypothesis that football-related brain damage is a factor in the suicides (and other neurological problems) is reasonable. It should be studied further. It’s possible - practically certain, in fact - that there are also other factors in each individual case.