If people are interested in this, I would really recommending taking a gander at Emile Durkheim's 'Suicide'. He was one of the first sociologists, and attempted to apply his methodology to what one might think the most private decision: suicide. After noticing that the annual rate of suicide was fairly stable, and varied from group to group, he tried to come up with a sociological explanation for this.

He has three categories of suicide:

• Egoistic: this occurs when people are poorly socially integrated - they feel isolated or lack social roots, This is similar to the type of thing mentioned by commenters who talked about the importance of religion.

• Altruistic: the opposite of egoistic (and far less common) - when value their group so much they are willing to sacrifice themselves for it.

• Anomic: this is the most interesting, and relevant to the original post. He claims that suicide can occur as a reaction to sudden jolting changes, upheaval and disequilibrium. This can happen with a sudden loss or a sudden gain in status/wealth/etc: you get anomic suicides in busts (bankers jumping out of windows) and booms (lottery winners who can't handle their new situation).

Of course there's quite a bit to criticize him about, but it's very interesting stuff.