Cal State Long Beach. File photo.

Cal State Long Beach researchers studying the causes of postpartum depression have found an association between the disorder and elevated levels of the stress hormone cortisol.

Cortisol, which helps with fetal organ development, typically rises during a woman’s pregnancy and then drops after she gives birth. But some women do not experience that sudden drop in cortisol levels, leaving them more at risk for postpartum depression, researchers found.

CSULB psychology professor and researcher Guido Urizar Jr. said the study is one of the first to suggest that women who have higher postpartum cortisol levels are at greater risk of symptoms for postpartum depression.

“We were able to identify at which times, during pregnancy and postpartum, that altered cortisol levels and elevated stress in mothers were most strongly associated with postpartum depression, which has been shown in previous studies to have detrimental effects on the development of their infants,” he said in a statement.

The findings, published in the Archive of Women’s Mental Health, are the result of a four-year study examining cortisol levels in a hundred low-income women who participated in a prenatal stress management program.

As part of the study, participants shared their perceptions of personal stress during interviews in each trimester of pregnancy, as well as any symptoms of postpartum depression three months after giving birth. The women also collected saliva samples to measure their cortisol levels.

Overall, researchers found that women who had reported higher stress levels throughout pregnancy and after giving birth, as well as women who did not experience a drop in their postpartum cortisol, had higher rates of postpartum depression.

Researchers are now using the information to study the effectiveness of stress management for reducing the risk of postpartum depression.