Healthy new moms are less focused on non-baby stresses than women that are not mothers.

“We were interested in trying to understand why new mothers seem less stressed out,” says neuroscientist Heather A. Rupp of the Kinsey Institute for Research in Sex, Gender, and Reproduction. Rupp and her colleagues from the Kinsey Institute and the University of Zurich published the results of their study September 6 online in Social Cognitive and Affective Neuroscience.

Rupp and colleagues guessed that the hormone oxytocin might regulate the decreased response to stress in new mothers’ brains. They used functional MRI, an imaging technique that correlates activation in different brain areas to changes in blood flow, and compared the brains of non-mothers to mothers while the groups of women looked at emotionally-evocative negative images. They also exposed a subset of both groups to oxytocin via nasal spray.

One part of the brain, the right amygdala, was less responsive to the negative images in the moms than the non-moms, but only in the women that did not receive oxytocin. When the women received oxytocin, the brains of both moms and non-moms showed no difference in the right amygdala, with both groups showing fairly low activation.

When the team initially designed the study, Rupp “had high hopes that the oxytocin nasal spray would have really strong effects,” thus a lack of activation difference in the moms and non-moms who received the hormone raises questions worth investigating. According to Rupp, the effects of oxytocin turn out to be “more interesting and complex” than previously believed.

Most hormones are thought to function immediately and with predictable outcomes. Rupp notes, “With this study and some other work since then, it becomes a lot more clear that oxytocin’s role is very much modulated by the social context and the environment of the individual.” Understanding the window of time during which oxytocin functions as well as its social and environmental influences are obvious future directions for study.

In the case of the brains of the new mothers, their amygdalae might not have responded to the oxytocin because the hormonal environment had already been altered through the processes of carrying, birthing, and caring for their babies. Perhaps their brains were already saturated with oxytocin. Alternatively, the amygdala’s ability to respond might have shifted because the landscape of proteins responsible for recognizing the hormone changed.

The take home message, though, is that healthy women who have recently given birth have a buffered response to stress as compared to non-mothers. “This reduction in stress in healthy moms might have implications for women who have postpartum depression or anxiety disorders, which could help in treating them,” Rupp says.

Rupp predicts that the brains of women with postpartum depression would react to stress similarly to the brains of non-moms. Therefore, increasing oxytocin, either synthetically or in natural ways like getting a massage, may turn out to be an effective treatment for postpartum depression.


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