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Nighttime Breastfeeding: How Does It Affect Maternal Mental Health?

There is a movement afoot in childbirth education and perinatal health, urging mothers to avoid nighttime breastfeeding to decrease their risk for postpartum depression. We know that if mothers follow this advice, it will have a negative impact on breastfeeding. But let’s put that issue aside for the moment, and consider whether avoiding nighttime breastfeeding will preserve women’s mental health by allowing them to get more sleep. In short, is this good advice?

At first glance, it may seem to be. Since breast milk is lower in fat and protein than formula, we might assume that breastfeeding mothers sleep less than their formula-feeding counterparts. And when a mother’s mental health is at stake, avoiding nighttime breastfeeding might be worth the risk. However, recent research has revealed the opposite: Breastfeeding mothers actually get more sleep—particularly when the baby is in proximity to the mother. And that has major implications for their mental health. So if you want one more good reason for mothers to exclusively breastfeed their babies, there it is.

In a 2004 study of 33 mothers at four weeks postpartum, researchers Quillin and Glenn found that mothers who were breastfeeding slept more than mothers who were bottle-feeding. Data was collected via questionnaire that recorded five days of mother and newborn sleep. When comparing whether co-sleeping made a difference in total sleep, the researchers found that bedsharing, breastfeeding mothers got the most sleep, and breastfeeding mothers who didn’t share their beds got the least. Mothers who were bottle-feeding got the same amount of sleep whether their babies were with them or in another room.

Sleep patterns of 72 couples were compared up to one month postpartum via sleep diaries and wrist actigraphy. Most of the mothers (94 percent) were at least partially breastfeeding and 80 percent were exclusively breastfeeding. Most of the babies slept in their parents’ rooms, and 51 percent slept in their parents’ beds. Sleep and fatigue outcomes were not associated with type of birth, parent-infant bed-sharing, or the babies’ ages. Mothers who were exclusively breastfeeding had a greater number of nighttime wakings compared with mothers who were not breastfeeding exclusively. The exclusively breastfeeding mothers slept approximately 20 minutes longer than mothers not exclusively breastfeeding.

In a 2007 study of mothers and fathers at three months postpartum, data was collected via wrist actigraphy. The study compared sleep of exclusively breastfed infants versus those supplemented with formula. In this sample, 67 percent were breastfed exclusively, 23 percent were fed a combination of breast milk and formula, and 10 percent were exclusively formula fed. Mothers who exclusively breastfed slept an average of 40 minutes longer than mothers who supplemented, while mothers of formula-fed infants had more sleep disturbances. The researchers concluded that mothers who are supplementing with formula under the assumption that they are going to get more sleep should be encouraged to breastfeed so they will get an extra 30-45 minutes of sleep per night.

Not only do breastfeeding mothers get more sleep, but the sleep they get is of better quality. A 2002 study compared 12 exclusively breastfeeding women, 12 age-matched control women, and seven women who were exclusively bottle-feeding. They found that total sleep time and REM sleep time were similar in the three groups of women. The marked difference between the groups was in the amount of slow-wave sleep (SWS). The breastfeeding mothers got an average of 182 minutes of SWS. Women in the control group had an average of 86 minutes. And the exclusively bottle-feeding women averaged 63 minutes. Among the breastfeeding women, there was a compensatory reduction in light, non-REM sleep. Slow-wave sleep is an important marker of sleep quality, and those with a lower percentage of slow-wave sleep report more daytime fatigue.

The most recent study was published in Sleep, a major sleep-medicine journal not necessarily known for its support of breastfeeding. The 2009 study included 2,830 women at 7 weeks postpartum. It found that disrupted sleep was a major risk factor for postpartum depression. But here’s where it really gets interesting. When considering what disrupted sleep, the researchers found that the following factors were related to disturbed sleep: depression, previous sleep problems, being a first-time mother, a younger or male infant, and not exclusively breastfeeding. In other words, mothers who were not exclusively breastfeeding had more disrupted sleep and a higher risk of depression.

The results of these studies are remarkably consistent. Breastfeeding mothers are less tired and get more sleep than their formula- or mixed-feeding counterparts—and this lowers their risk for depression. Doan and colleagues noted that using supplementation as a coping strategy for minimizing sleep loss can actually be detrimental because of its impact on prolactin hormone production and secretion. Breastfeeding continuation and success, as well as deep restorative sleep, may be greatly compromised for new mothers who supplement during the night with formula.

In sum, advising women to avoid nighttime breastfeeding to lessen their risk of depression is not medically sound. In fact, if women follow this advice, it may actually increase their risk of depression.

About the Author:

Kathleen Kendall-Tackett is a health psychologist and international board-certified lactation consultant. She is clinical associate professor of pediatrics at Texas Tech University School of Medicine in Amarillo, Texas, and editor-in-chief of Clinical Lactation. Dr. Kendall-Tackett is author of more than 260 articles, book chapters and other publications, and is author or editor of 20 books on the subjects of maternal depression, trauma and breastfeeding. She can be found online at