All new mothers experience some sleep loss following childbirth, as their estrogen and progesterone hormone levels plunge. They typically spend 20 percent more of the day awake than average during the first six weeks after giving birth.

Study author Bobbie Posmontier of Drexel University in Philadelphia compared sleep patterns of 46 post-partum women -- half with symptoms of post-partum depression and half without. Sleep patterns were monitored for seven consecutive days.

Results showed that mothers suffering from post-partum depression took longer to fall asleep and slept for shorter periods. The worse their sleep quality, the worse their depression.

Sleep deprivation can hamper a mother's ability to care for her infant, as judgment and concentration decline. Sleep-deprived mothers may inadvertently compromise their infants' sleep quality because infants often adopt their mothers' circadian sleep rhythms.

Posmontier recommends that clinicians treating women for post-partum depression address the importance of adequate sleep.

The findings are published in the Journal of Obstetric, Gynecologic, & Neonatal Nursing.