Here is a fascinating study found by EmmaB:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1414751/

Seems to indicate both genetic and financial causes.

I did find an interesting study but can't put my hands on it now stating that men are 3X more likely to commit suicide than women BUT woman are 5X more likely than men to try. The method of suicide is part of the reason - men choose guns which can be very effective vs poison or prescription drug overdoe (the women's choice). I wonder how much of this is related to families protecting a daughter's reputation by hiding a suicide. In fact, I would have to believe that the statistics in Emma's find are way off since some countries for religious and cultural reasons abhor suicide.