Leslie, I agree with you about high risk factors.  I see a lot of mothers
in this category in my LLL group of mothers nursing twins.  Many are
"older" first time mothers with very successful careers as lawyers,
university professors, etc.  All the things that have made them successful
in their work, like being well organized and approaching problems
intellectually, are called into question with new baby twins who may also
be premature.  These mothers often have read a great deal about mothering,
but they are not prepared for the total disruption of their previously
well-organized lives that comes with the birth of their babies.  I think
their sense of self-esteem is closely tied to handling everything
beautifully.  Exhausted, unable to meet everyone's needs and demands at
once, they feel totally out of control.  It is very hard for them to accept
help and to give up attending to all the details they used to be
responsible for. (I know, because I was also one of these mothers a few
years ago).   Even more difficult is the situation where there is also one
older child, age 2 or 3.  These mothers feel very guilty about not
perfectly meeting everybody's needs all the time.
It does seem to really help when these mothers get together and talk about
how they are feeling.  They share their stories and tears and support each
other tremendously.
I also feel an added factor that makes it especially hard for "first world"
women is their lack of experience with new babies.  As Kathy Dettwyler
pointed out, the young women in Mali and other third world cultures have
been intimately involved in caring for younger siblings throughout their
own growing up.  They know what to expect from babies, what their needs and
behaviors are like, how to care for them.  They therefore don't have the
unrealistic expectations of new mothers we see here.
Anne Altshuler, RN, MS, IBCLC and LLL leader in Madison, WI (My own twins
recently turned 12!)