According to an article in Medical News Today called "Depression Turns Off The Music in the Mother-Baby Dance," depressed moms respond less sensitively and more negatively to their infants:

As part of a study funded by the Canadian Institutes of Health Research (CIHR), Dr. Alison Fleming, together with her student, Andrea Gonzalez, and collaborator, Meir Steiner, played recordings of newborns’ cries. Depressed women, she says, showed more anxiety in response to the pain cry than new mothers who aren’t depressed.

"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."

Fleming wants to know more about why women with post-partum depression respond so differently to their babies. So for her next research study (also funded by CIHR), she and her colleagues will use functional magnetic resonance imaging, or fMRI, to see what is happening in the brains of depressed and non-depressed mothers while they look at pictures or hear cries of their babies. A better understanding of how the brain functions in women with postpartum depression could lead to possible interventions, as well as programs to prevent the depression and assist in child development.

I know in my case my son seemed to cry incessantly. He had colic. Did I cause the colic by my extreme anxiety, or did the colic give me extreme anxiety? Did I overreact to his crying? Was I more stressed out by it than the "normal" mom? I had such a hard time when he was upset. I would physically feel like curling up into a ball and hiding in a dark closet. I felt like I couldn’t handle it and had no idea how to help him feel better, and that it was my fault if I couldn’t get him to stop. I’m glad they are doing this research.