First-time research at Ohio State involving pregnant rats suggests a mother’s stress during pregnancy may contribute to postpartum depression.
Benedetta Leuner, associate professor of psychology, and Kathryn Lenz, assistant professor of psychology, found that chronic stress during pregnancy can trigger a response in the brain that can alter functions and contributes to postpartum depression — a condition that affects 1 in 10 mothers, according to the Cleveland Clinic. The condition can cause extreme sadness, anxiety and exhaustion after a mother has her baby, according to the National Institute of Mental Health.
“We know that stress can affect immune function, including immune function in the brain,” Leuner said. “We know that stress is a major predictor of whether women develop postpartum depression or not, and so we wanted to know how stress would alter this maternal immune environment.”
The foundation for the work was based on the idea that during pregnancy, there is an increase in the output of anti-inflammatory cytokines and a decrease of microglia — cells involved in brain connections. The two immune cell fluctuations combined suggest that the brain might be assuming a protective anti-inflammatory state, Leuner said.
During its development, the brain grows, refines and changes its connections, Lenz said. In pregnancy, there’s similar repatterning of the adult brain, which is important for motherhood, as they have specific behaviors and needs they didn’t before, she said.
“We know that cells like microglia are crucial to that normal process of wiring and setting up the proper connections of the brain,” Lenz said. “It was previously unknown whether if the immune cells that we know are responsible for setting up the brain wiring are just as important for remodeling the brain when it’s time to be a new mother.”
The study, funded by the National Institutes of Health, was a collaboration between two labs in the psychology department. The research concluded in spring 2019 and is currently being written up for publication, Lenz said.
Lenz said her lab focused on the brain development and what factors influence it, while Leuner said her lab was interested in stress and mood disturbances in new mothers.
“We exposed pregnant rats to a stress procedure, and we’ve shown that induces behaviors after they deliver that are similar that you’d see in [a] mom’s postpartum depression,” Leuner said.
She said they looked at rat mothers about a week after they gave birth, which is when symptoms of postpartum depression are typically heightened.
The symptoms can interfere with a mother’s ability to care for her baby and herself, Leuner said. The rodents didn’t want to drink their sugar water anymore and weren’t taking care of their babies, which reflect changes seen in humans.
“We looked at the immune systems of these stressed moms and found that instead of being anti-inflammatory, things shifted to a more inflammatory state,” Leuner said. “Microglia numbers went up, increased expressions of pro-inflammatory cytokine numbers went up, so we are thinking that maybe this could be a brain mechanism that’s underlying mood disorders during this depression period.”
Lenz said microglia eat up synaptic material, which is responsible for communicating between neurons, and also have an effect on the brain. Leuner said this suggested that what’s happening in the body and brain can be completely different, and it can’t be assumed that what is seen in the blood is happening in the brain.
“The surprising thing was when we looked at some [of] those inflammatory markers in the blood of stressed moms, we saw no changes,” Leuner said. “Some inflammatory cytokines that were increased in the brain weren’t increased at all in the blood.”
Some of the changes observed are specific to motherhood, and in previous research, Leuner said using stress on nonmothers did not trigger the behavioral despair and brain changes they saw with the rat mothers.
“We have to connect all the information from previous research with this new information,” Leuner said. “We have to see if all of these things are linked together.”