Lead author Dr. Katherine L. Wisner, a professor at Northwestern Medicine in Chicago, said the study involved a depression screening of 10,000 women who had recently delivered infants at single hospital.
"In the United States, the vast majority of postpartum women with depression are not identified or treated even though they are at higher risk for psychiatric disorders," Wisner said in a statement. "It's a huge public health problem. A woman's mental health has a profound effect on fetal development as well as her child's physical and emotional development."
The study, published in the Journal of the American Medical Association, also found 30 percent of women had depression onset prior to pregnancy, 40 percent postpartum and 30 percent during pregnancy.
"Most of these women would not have been screened and therefore would not have been identified as seriously at risk," Wisner said. "We believe screening will save lives." Wisner conducted the research when she was at the University of Pittsburgh.
Of the about 1,400 new mothers screened positive for depression, 826 received full psychiatric assessments during at-home visits. In women who screened positive for depression, 19 percent said they thought of harming themselves.
Suicide accounted for about 20 percent of postpartum deaths and is the second most common cause of mortality in postpartum women, Wisner said.