Here in the UK one person every week jumps in front of a tube ( London underground).
I don't know this for a fact, but I was told this by my last psychitrist a few years ago. I was then in a very bad state, lots of bad memory, flash backs, very traumatized basically.
The lady asked me how come I never took my own life, I had to think about that, I realized that the thought never enterd my mind. However I think what would stop me from doing that is the thought that those we care about the most will suffer the most, and that reason alone is enough to stop me and any other SANE person from ending it.
Of course I might be wrong.