Hi David,
I've beem meaning to reply to this post as it's one I've had some inteerst in in the past. I managed to find a few papers via the British Journal of Psychiatry that I've come across before and they highlight some of the relevant issues
http://bjp.rcpsych.org/content/184/1/10.full
http://apt.rcpsych.org/content/10/1/13.short
I think it definitely boils down to culture. With growing globalisation, especially when it comes down to ethnic minorities in more devloped countries, it can pose considerable stresses on migrants, and where they do not have the luxury of the social support structures in terms of close knit communities of family and friends they are used to, it is so much easier to fall into depression.
I came across an interesting statistic in the past also that said something along the lines of although black women are prone to post natal depression, it is not documeted as being that prevalent amongst them, probably because of cultural norms and the stigma associated with it. Every woman, especially in out culture wants to be seen as capable of coping with the demands of motherhood. Also I read (these quotes tends to stick with me being of AfroCaribbean descent myself lol) that the rates of suicide are the lowest amongst the same group - AfroCaribbean women. It begs the question of why? & I think in the end of definitely boils down to cultures, way of life and support structures, which tend to lack amongst minority and ethnic populations in more developed countries, from what they are used to 'back home'.
