Postpartum Depression's Lingering Toll

Postpartum depression can make you feel, quite frankly, insane.

Psychosis, PTSD and other serious mental illnesses have been linked to that fraught post-childbirth period. (According to the group Postpartum Support International 15-20 percent of pregnant women and new mothers will experience a maternal mental health disorder.)

Most recently, of course, Miriam Carey, a 34-year old dental hygienist, rammed her car — with her one-year old baby inside — into police barricades near the White House. We don't know exactly what was going in in Carey's brain — maybe she had a previous mental illness, maybe she was taking medication for it.

Whatever happened, one thing is certain: having a baby changes your brain. And under stress, those changes can be negative and long-lasting.

New research on mother rats found that exposure to chronic stress early in life (in this case an unfamiliar male intruder) "not only impairs a mother’s ability to care for her own children but can also negatively impact her daughter’s ability to provide maternal care to future offspring."

Here are more details from the the Tufts University Cummings School of Veterinary Medicine news release:

A different male rat was placed in the cage of the first-generation mothers and their newly born pups for an hour a day for 15 days. Consistent with previous research, the lactating mother rats responded to the stress of the intruder with depressed maternal care, impaired lactation, and increased anxiety. The pups of these mothers were also exposed to the conflict between their mothers and the male intruders.

After reaching maturation, second-generation females were mated and compared to a control group where neither the mother nor the pups had been exposed to a male intruder. The second generation mothers that experienced the early life stress also displayed depressed maternal care, impaired lactation, and increased anxiety. There were also changes to hormone levels: an increase in the stress hormone corticosterone, and decreases in oxytocin, prolactin (important to both maternal behavior and lactation) and estradiol.

I asked study author Ben Nephew, an assistant professor in the department of biomedical sciences at Tufts' Cummings School of Veterinary Medicine, about the research,

specifically the overall takeaway, any surprise findings and how a rat study might translate to humans. Here's his emailed response, lightly edited:

1. The major conclusion is that we have created an animal model that can help us better understand postpartum depression and anxiety, as well as depression and anxiety in the offspring of depressed mothers. What we saw in the rats is that exposure to social stress (the male intruder) not only impairs a mother’s ability to care for her children but can also negatively impact her daughter’s ability to provide maternal care to future offspring. This model, which mimics many features of human depression through the use of social stress, can be used to develop improved preventative measures and treatments.

2. We were surprised at several of the results. The increase in stress-related restlessness, a specific feature of postpartum depression, was particularly interesting. The effects on maternal behavior were very significant compared with other studies. I think the restlessness increased due to the stress-related changes in the brain and hormones of the stressed rat moms. Maternal care (staying with the pups on the nest) is less rewarding, and the stressed moms may also be more reactive to other sensory stimuli in their environment. As a result, they spend less time with their pups, and more time wandering around the cage. It also seems like they have impaired decision making, which is actually another specific feature of postpartum depression in humans. Maternal rats typically retrieve their pups to the nest, groom them, and then nurse, in a regular pattern. The stressed dams will pick up pups and drop them all over the cage, move the nest after settling down to nurse, or settle down to nurse without gathering all the pups first.

We also saw a substantial decrease in how much milk the pups were getting from their mothers. Few animal studies of postpartum depression investigate lactation despite the observation that depressed women often have difficulties with breastfeeding. We were also surprised at how similar our hormone data were to data from human studies.

3. The pathways in the brain and the hormones that control maternal behavior in rats and humans are very similar. Exposure to social stress can cause depression in both rats and humans. Our research can translate to humans through the use of social stress models to develop new preventative measures and treatments for depression and anxiety. For example, we can test the effectiveness of increased social support and/or various pharmaceutical targets identified in both our model and clinical studies. Some of these pharmaceutical targets, such as oxytocin, vasopressin, and prolactin are already commonly used in humans, so the development of human treatments based on these targets could be rapid.

And if you still think this phenomenon is specific to rats, think again. New research published in JAMA Psychiatry yesterday found that depression in pregnant women appears to increase the risk that their children will likely suffer from depression when they're 18 years old. From the JAMA news release:

Rebecca M. Pearson, Ph.D., of the University of Bristol, United Kingdom, and colleagues examined possible associations between prenatal and postnatal depression in women and later depression of their children at age 18. Researchers analyzed a UK community-based study population with data from more than 4,500 parents and their adolescent children.

Study findings indicate that children were more likely to have depression at age 18 if their mothers were depressed during the pregnancy...