I, too, often wonder what the widespread, greater effects of societal lack of breastfeeding are.  Some of my concerns are that the dissolving family, high rates of child abuse and neglect, violence, etc., etc. are related to the altered mother-child relationship that generally accompanies lack of BF.  (If nothing else, hormonal aspects of that relationship are affected, and most of us would agree, I think, that the effect is broader.)  This sense that lack of breastfeeding may well have a role in the creation and continuation of the great societal changes (for the worse) of this century is one of the things that seems to set me apart as a BF "loony".  I am seldom accused of "pushing" mothers to BF, or of being a zealot who makes others uncomfortable - as I have read that some of you face at work - but just thought of as a kook when I am unwise enough to air my beliefs.  And yet, I think it makes *perfect* sense that ignoring the natural, evolution-proven way to feed human babies could utterly (no pun) disrupt the evolution of society.  Ah, well...
Anyway, I just wanted to interject that although my sibs and I (born in the '50s) were all BF for our first 9 mo -a long time in that era - and never had ABM, 2 of 3 of us have had long-term problems with depression and only feel well on SSRIs (serotonin re-uptake inhibitors, like Zoloft).  The 3rd has rare but severe panic attacks.  And my eldest, BF for a year and exposed to a very little ABM (if only I knew then what I know now...) also has suffered with depression for years and needs - but usually won't take - SSRIs (teenagers...).  So in my small case study, even the BF can have screwed-up brain chemistry.  In this case I suppose it is genetic.  For those who would worry, we do all *also* get psychotherapy :)  Not just pill-poppers, but couch-hoppers, too!
Sorry this is so long.  I'll go back to lurking.
Willow