Scientists at U.C. Irvine say women who developed postpartum depression had higher levels of a certain hormone, called pCRH during pregnancy.
They believe that the sudden loss of this hormone during birth may trigger the depression.
About one in 10 mothers experience post-partum depression after the birth of a child.
New research on post-partum depression may one day lead to a screening process to tell which expectant mothers are more likely to develop the condition.