Well for me, when my son started cutting back nursings was about when my depression started to lift...but I never did get that rush of whatever hormone-caused good feelings, I was pretty depressed!
I think the hormones affect different people differently. I think for me they actually serve to deepen the depression, and it takes more work for me to feel happy. Also I am one of those people who don't lose weight while breastfeeding, don't know if the two are linked or not?