THURSDAY, Sept. 16 (HealthDay News) -- Women with postpartum depression have differences in brain functioning that may interfere not only with how they process their own emotions, but also with their ability to be responsive to the emotions of their infants, new research suggests.

In a small study that involved MRI brain scans, researchers at the University of Pittsburgh Medical Center revealed that women with postpartum depression have reduced activity in parts of the brain that control emotional responses and recognize emotional cues in others.

"Our study provides a brain basis for what has been described in clinical settings and behavioral studies, which is that women with postpartum depression may have reduced activity in regions of the brain that process emotions and that are involved in being attuned to others' emotions," said study author Dr. Eydie L. Moses-Kolko, an assistant professor of psychiatry at the University of Pittsburgh School of Medicine. These brain abnormalities may help explain why mothers with postpartum depression often have problems bonding with their infants, she noted.

Postpartum depression, which affects an estimated 15 percent of new moms, is different than the typical "baby blues" that often occur after delivery, when a new mother may burst into tears at the drop of a hat, experts said.

While the baby blues usually go away within two weeks of giving birth, postpartum depression can continue for months and often causes such strong feelings of sadness, anxiety or despair that a woman has trouble coping with her daily tasks. Previous research has shown that maternal depression can negatively affect an infant's mental and physical development.

Moses-Kolko and her colleagues studied 14 depressed and 16 healthy mothers, all of whom delivered a healthy term infant in the preceding 12 weeks, were medication-free and had previously given birth to another child. The mothers were shown images of angry and scared faces, and the researchers examined their neural reactions to the pictures with the use of MRI scans. The mothers also filled out questionnaires that assessed their attachment quality, hostility and pleasure in interaction with their infants.

The researchers found that negative emotional faces activated the left dorsomedial prefrontal cortex, which is a social cognition region of the brain, significantly less in depressed mothers than in healthy mothers. Deficits in this region, they said, might represent diminished awareness of the emotions of others and less empathy for them. Another key finding was that when the women saw negative images, communication between the left dorsomedial prefrontal cortex and the left amygdala was present in healthy moms but not in the depressed ones, suggesting that this might be an important neural circuit that regulates emotional response to unpleasant sounds, such as a baby's cry.

The study, which was partly funded by the U.S. National Institute of Mental Health and the National Alliance for Research on Schizophrenia and Depression, was published Sept. 15 in the online advance edition of the American Journal of Psychiatry.

Moses-Kolko said more research is needed "to determine what brain patterns are predictive of response to an array of treatments including psychotherapy, medications or hormones."

"This is a very interesting study, but it's really just the beginning," said Michael W. O'Hara, a professor of psychology at the University of Iowa in Iowa City, who specializes in perinatal depression. "More studies need to be done in a much larger sample of women, to see if the results can be replicated."

O'Hara added: "It's my belief that postpartum depression is a heterogeneous disorder that includes depression that is coincidental with childbirth, and depression that is inextricably related to it." Future MRI studies need to differentiate between these two groups of women, he said, because "if we mix these two samples together, it may obscure the true findings."

More information

For more on postpartum depression, visit the U.S. National Library of Medicine.