Freakanomics did a good podcast on suicide. This question was addressed at least a little, by talking about the apparent rareness of suicide in some cultures:
http://www.freakonomics.com/2011/08/31/new-freakonomics-radi...Some Googling turned up this study, http://www.ncbi.nlm.nih.gov/pubmed/16420711, "The association between suicide and the socio-economic characteristics of geographical areas: a systematic review". At first I thought their conclusions were clear, but I find I have difficulty understanding subsequent sentences with respect to each other. I'm afraid I would need to read the whole paper to understand exactly what their conclusions are.
