Some risk factors for postpartum depression are well documented. They
include anxiety, stress, lack of social support, low self-esteem, depression
before or during pregnancy, a history of premenstrual syndrome, and a history
of oral contraceptive—induced mood changes.
A biological marker for postpartum depression may now have been discovered
as well. The marker is an elevated level of the hypothalamic hormone
corticotropin-releasing hormone (CRH) during the 25th week of pregnancy.
The finding was reported in the February Archives of General
Psychiatry. The lead investigator was Ilona Yim, Ph.D., an assistant
professor of psychology and social behavior at the University of California,
CRH is known to play an important role in the origin of depression in the
non-pregnant state. CRH levels are also known to soar during pregnancy. Yim
and her coworkers suspected that a surge of CRH during pregnancy might help
set the stage for postpartum depression in some women, so they launched a
longitudinal cohort study to test the hypothesis.
One hundred pregnant women were recruited into the study. Blood samples
were obtained at 15, 19, 25, 31, and 37 weeks of pregnancy from each of the
women. The blood samples were screened not just for CRH, but for the pituitary
hormone adrenocorticotropic hormone (ACTH), which is regulated by CRH, and for
the adrenal cortex hormone cortisol, which is regulated by ACTH. Each woman
was assessed for depressive symptoms four times during pregnancy and on
average nine weeks after delivery. Out of the 100 women, 16 developed
postpartum depression symptoms.
After taking prenatal depressive symptoms into consideration, the
researchers looked to see whether there was any link between pregnancy levels
of CRH, ACTH, or cortisol and the development of postpartum depression
symptoms. They found only one link, and that concerned CRH. An elevated level
of CRH at 25 weeks of pregnancy was a highly significant predictor of
postpartum depression—that is, it predicted postpartum depression with
an accuracy of 75 percent and with a misclassification rate of 24 percent.
Although Yim and her colleagues had anticipated that CRH might predict
postpartum depression, she "was surprised at how robust this finding
was," Yim told Psychiatric News. "I also did not
anticipate a timing effect. I would have speculated that overall CRH exposure
throughout pregnancy would play a bigger role."
Yim and her group will now attempt to replicate their findings. If they
manage to do so, and if other groups manage to do so as well, "it may be
considered useful to implement a CRH-postpartum depression screen into
standard prenatal care," they wrote in their study report."
Because blood draws to screen for gestational diabetes are typically
performed at 24 to 28 weeks of gestation, a potential postpartum depression
screen could be completed at the same time."
Meanwhile, Yim and her colleagues will attempt to determine why a large
surge in CRH around 25 weeks of pregnancy seems to predict postpartum
depression. They do know that the placenta starts to churn out large amounts
of CRH around this time, supplementing the amount of CRH that is already being
made by the hypothalamus. But why many women who develop postpartum depression
tend to produce even more CRH at 25 weeks of pregnancy than do women who do
not develop postpartum depression is not clear.
"This work is an exciting contribution in the area of postpartum
depression," Marlene Freeman, M.D., told Psychiatric News."
It supports [the notion] that women who suffer from postpartum
depression have a biological vulnerability, and that risk may be assessed
during pregnancy at a specific point. It would be important to build upon this
work to determine how women at risk for postpartum major depressive episodes
might be clearly identified for careful monitoring, early treatment, and even
Freeman is a psychiatrist with a focus on the interface between psychiatry
and obstetrics. She is affiliated with the Perinatal and Reproductive
Psychiatry Clinical Research Program at Massachusetts General Hospital.
The study was funded by the National Institute of Child Health and Human
An abstract of "Risk of Postpartum Depressive Symptoms With
Elevated Corticotropin-Releasing Hormone in Human Pregnancy" is posted