Why is it that depression is more prevalent in western societies?

I spent half of my childhood in west africa till i came to the US at age 14, and it puzzles me as to why everyone over there is happy and there is a sense of community and love around and here in the US is the total opposite? i hear of countless suicides and depression and antidepressants....why is this?? I mean with all the goodies hee in the states why the depression? amd people in 3rd world countries are happy and content?