Women who have higher levels of a hormone produced by the placenta midway through their pregnancy appear more likely to develop postpartum depression, according to a report in the February issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Postpartum depression (PPD) is more serious than "baby blues" and begins within four to six weeks of giving birth, according to background information in the article. Risk factors include a history of depression, stressful life events, a lack of social support, low self-esteem and depression, anxiety or stress during pregnancy. However, these risk factors explain only a portion of the differences between women who develop PPD and those who do not.

"Endocrine risk factors for PPD have been identified as well, including changes in reproductive hormones during pregnancy, a history of premenstrual syndrome and a history of oral contraceptive-induced mood changes," the authors write. A possible link between a hormone produced by the placenta, known as placental corticotropin-releasing hormone (pCRH), and PPD has also been hypothesized. Ilona S. Yim, Ph.D., of the University of California, Irvine, and colleagues studied this hormone in 100 pregnant women who visited two southern California medical centers during the study period. Blood samples were taken at 15, 19, 25, 31 and 37 weeks' gestational age, and symptoms of depression were assessed at the last four pregnancy visits and again an average of 8.7 weeks after delivery.

A total of 16 women developed PPD symptoms at the follow-up visit. Levels of pCRH when the women were 25 weeks pregnant strongly predicted the development of PPD. A cutoff of 56.86 picograms of pCRH per milliliter of blood has a sensitivity of 0.75 and a specificity of 0.74 for PPD, meaning that about three-fourths of women with future PPD would be identified using this marker and only 24 percent of women would be misclassified. The predictive capability of the hormone levels increased when midpregnancy depressive symptoms were also assessed.

The narrow window of time in which pCRH levels predicted PPD symptoms-at 23 to 26 weeks' gestational age-roughly coincides with a surge in levels of the hormone. "We do not know which factors may precipitate the surge in pCRH, but some evidence suggests an association between elevated cortisol [stress hormone] early in pregnancy and increased pCRH late in pregnancy," the authors write.

"Our study has important clinical and theoretical implications," they continue. "If our results are replicable, it may be considered useful to implement a pCRH PPD screen into standard prenatal care. Because blood draws to screen for gestational diabetes are typically performed at 24 to 28 weeks' gestational age, a potential PPD screen could be completed at the same time. In addition, a better understanding of the role of pCRH in the pathophysiologic mechanism leading to PPD may contribute to the development of preventions targeted at this rather common disorder."

Arch Gen Psychiatry. 2009;66[2]:162-169.

Archives of General Psychiatry