How Can Prenatal Stress Cause Postpartum Depression?

Whether or not you're expecting, you can feel the effects of stress in your body. But chronic stress during pregnancy can also change your brain, say researchers from Ohio State University. And by getting in the way of key "brain benefits" connected with motherhood, stress can make it more likely for new moms to develop postpartum depression (PPD).

To learn more about the far-reaching effects of prenatal stress, OSU researchers conducted a study that looked at changes in brain cells and brain activity among a group of mother rats. According to their results, when rats were exposed to normal amounts of stress during pregnancy, parts of brain cells used to exchange information with other neurons increased by almost 20 percent. This boost, researchers say, improves cognitive functioning in moms, especially multitasking. It's believed that the brains of human mothers undergo similar changes.

In contrast, the brains of mother rats that led more stress-filled lives during pregnancy did not show this same increase. And, researchers noted, after their babies were born these rats had less physical interaction with their babies—the same observation often made about human mothers experiencing postpartum depression.

"Animal mothers in our research that are unstressed show an increase in the number of connections between neurons," says Dr. Benedetta Leuner, an assistant professor of psychology and neuroscience at Ohio State University. "Stressed mothers don't." Dr. Leuner says the difference "makes the stressed mothers more vulnerable [to depression]."

As an example, Leuner describes that "after separation from pups for 30 minutes, unstressed mothers would gather up their babies, put them in the nest and nurse them"—an example of multi-tasking. On the other hand, "stressed mother rats left the pups scattered around, wandered around the cage and fed the babies less frequently," closely mimicking some of the symptoms that are seen in women with postpartum depression, she finds.

So what's a stressed-out human mom to do? "I think this is a sign I need to take more naps and finally go for a massage," jokes busy mom-to-be Sarah Bond of Glen Cove, New York.

But on a more serious note, Bond wonders whether more attention to mental health during pregnancy is needed during prenatal care. "How much weight we've gained is such a big deal at every prenatal check up," says Bond. "But how about talking about how stressed out we are? I often feel like I have the weight of the world on my shoulders, but never know if I should bring this up."