To post-partum depression, add another neurochemical pitfall of mothering: post-weaning depression. Blogger Jen Eyer examines her experience of "breastfeeding withdrawal" on Neurotic Mom.
Now that I think about it, it really isn't surprising that even a decrease in nursing would cause my mood to drop. Less nursing = less oxytocin, aka the "love hormone." It's going to take time to adjust to the withdrawal.
It sounds like Jen has a wonderful and supportive husband. But she's forgetting a possible replacement for the oxytocin she's missing: sex and orgasm.