According to this article, new research suggests mothers with post-partum depression tend to respond differently than non-depressed mothers to the cries of their babies, particularly cries suggesting pain. The response by the mother with post-partum depression to a cry indicating pain involves significantly more anxiety. This anxiety impairs the mother's ability to soothe the child and cope with the child's distress. This impairment in the mother's response interrupts the "dance" between the mother and infant. This might, if prolonged, impact the child's development. From the article:
"We know that, compared to non-depressed mothers, depressed moms respond less sensitively and more negatively to their infants," says Fleming, a researcher from the University of Toronto (Mississauga). "In this case, their anxiety and their negative feelings could affect their ability to soothe their babies and cope with their distress."
Fleming describes the mother-baby relationship as a dance: baby smiles, mom smiles back; baby vocalizes, mom vocalizes back. Depressed mothers, she has found, have more difficulty interacting with their babies - they don't take part in the dance, as it were.
"They may show little positive affect," she says. "Or they may become agitated and overly - but inappropriately - responsive."
The research, conducted in Canada, notes the cultural and geographic aspects that impact post-partum depression in that country (less connected families, longer winters with more darkness). It also notes the benefits of addressing behavioral and interpersonal aspects of the depression with this quote:
But the best prescription for post-partum depression, Fleming says, at least in less severe cases, could be as simple as getting out of the house, spending more time with other people and soliciting support from family and friends.
I'm always encouraged when the behavioral and interpersonal aspects of depression are addressed, especially in the context of treatment. What isn't mentioned in the article is the role a father (as well as other caretakers) can play, both in engaging in "the dance" with the child while the mother addresses her depression, as well as in helping the mother with her treatment. Having gone through the process of having two children with my wife, even the best doctors have paid only lip service to my role in monitoring my wife's mood for signs of depression, how to help her cope with the difficulties associated with both pregnancy and post-partum issues, or other issues related to this topic (aside from the occasional "And do you have any questions?"). This would seem to me to be an area ripe for psychoeducation, as fathers could be a potentially significant source of support, as well as data for the doctor in assessing how well the mother is functioning.