It’ s not clear what causes postpartum depression. The condition, which is marked by persistent feelings of sadness, hopelessness, exhaustion and anxiety, usually begins within four weeks of giving birth and can persist for weeks, months or even up to a year. An estimated 10 to 18% of all new mothers develop the condition, and the rate rises to 30 to 35% among women with previously diagnosed mood disorders.
Scientists have long believed the symptoms were related to the large drop-off in the mother’s estrogen levels following childbirth, however studies have shown that both depressed and non-depressed women have similar estrogen levels.
Now researchers from Johns Hopkins say they have discovered alterations in two genes that, can reliably predict whether a woman will develop postpartum depression.
The genetic modifications, which alter the way genes function without changing the underlying DNA sequence, can apparently be detected in the blood of pregnant women during any trimester, potentially providing a simple way to foretell depression in the weeks after giving birth, and an opportunity to intervene before symptoms become debilitating.
By studying mice, the researchers suspected that estrogen induced genetic changes in cells of the hippocampus – the part of the brain that governs mood. They then created a complicated statistical model to find the candidate which could be potential predictors for postpartum depression. That process resulted in the identification of two genes, known as TTC9B and HP1BP3.
Little is known about these genes except for their involvement in hippocampal activity. However the team suspects that they may have something to do with the creation of new cells in the hippocampus and the ability of the brain to reorganize and adapt in the face of new environments. Both of these elements are known to be important in mood.
Furthermore, estrogen can behave like an antidepressant, so when it is inhibited, it adversely affects mood.
“Postpartum depression can be harmful to both mother and child,” says Zachary Kaminsky, Ph.D., an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine. “But we don’t have a reliable way to screen for the condition before it causes harm, and a test like this could be that way.”
The findings of the small study involving 52 pregnant women are described online in the journal Molecular Psychiatry.
The study involved looking for epigenetic changes tin the thousands of genes present in blood samples from 52 pregnant women with mood disorders. The women were followed both during and after pregnancy to see who developed postpartum depression.
The researchers noticed that women who developed postpartum depression exhibited stronger changes in those genes that are most responsive to estrogen, suggesting that these women are more sensitive to the hormone’s effects. Specifically, changes to the two genes – TTC9B and predicted with 85% certainty which women became ill.
“We were pretty surprised by how well the genes were correlated with postpartum depression,” Kaminsky says. “With more research, this could prove to be a powerful tool.”
Evidence suggests that early identification and treatment of postpartum depression can limit or prevent debilitating effects. Alerting women to the condition’s risk factors — as well as determining whether they have a previous history of the disorder, other mental illness and unusual stress — is key to preventing long-term problems.
Research also shows that postpartum depression not only affects the health and safety of the mother, but also her child’s mental, physical and behavioral health.
If the results of this preliminary work pan out then a blood test for the biomarkers could be added to the battery of tests women already undergo during pregnancy. More importantly, the results could help to inform decisions about the use of antidepressants. While there are concerns about the effects of these drugs on the fetus and their use should be weighed against the potentially debilitating consequences to both the mother and child of forgoing them.
As Kaminsky says “If you knew you were likely to develop postpartum depression, your decisions about managing your care could be made more clearly.”