New mothers who successfully breastfeed their babies are less likely to get postnatal depression, new research suggests.
Expectant mothers who plan to breastfeed after they have given birth but are unable to are at the highest risk of developing the condition, experts found.
Around 13% of new mothers experience postpartum depression within 14 weeks of giving birth. As well as posing serious mental health problems for the mother it can also have significant affects on the newborn's cognitive, social and physical development, researchers said.
They said that the effect that breastfeeding has on postnatal depression is not well understood and set out to investigate whether there is a link between the two.
The authors, from the UK and Spain, surveyed women who had almost 14,000 babies in the Bristol area during the 1990s when their children were t wo, eight, 21 and 32 months old.
They also examined whether or not the women suffered depression during their pregnancy so they could take into account previous mental health conditions.
Their study, published in the journal Maternal and Child Health, found that mothers who planned to breastfeed and who actually went on to breastfeed were around 50% less likely to become depressed than mothers who had not planned to, and who did not, breastfeed.
Those who planned to breastfeed, but who did not go on to breastfeed, were more than twice as likely to become depressed as mothers who had not planned to and who did not, they found.
"For mothers who were not depressed during pregnancy, the lowest risk of postpartum depression was found among women who had planned to breastfeed, and who had actually breastfed their babies, while the highest risk was found among women who had planned to breastfeed and had not gone on to breastfeed," the authors wrote.
This link was found to be most pronounced when the babies were two months old but much smaller by the time they were eight months or older, they added.
The researchers from the University of Cambridge, Queen Mary University of London as well as an expert from the University of Seville in Spain, said that their study shows the benefits of breastfeeding to a new mother's mental health.
"Breastfeeding has well-established benefits to babies, in terms of their physical health and cognitive development; our study shows that it also benefits the mental health of mothers," said Dr Maria Iacovou, one of the authors from the University of Cambridge's Department of Sociology.
"In fact, the effects on mothers' mental health that we report in this study are also likely to have an impact on babies, since maternal depression has previously been shown to have negative effects on many aspects of children's development."
She added: " Lots of mothers and babies take to breastfeeding pretty easily. But for many others, it doesn't come naturally at all; for these mothers, having someone with the training, the skills, and perhaps most importantly the time to help them get it right, can make all the difference.
"However good the level of support that's provided, there will be some mothers who wanted to breastfeed and who don't manage to. It's clear that these mothers need a great deal of understanding and support; there is currently hardly any skilled specialist help for these mothers, and this is something else that health providers should be thinking about."
Cathy Warwick, chief executive of the Royal College of Midwives, said: "It i s vital (women) receive high-quality support immediately after the baby is born and throughout the postnatal period. The Royal College of Midwives (RCM) is actively campaigning to ensure there are adequate midwifery staffing levels to ensure appropriate support from well-trained staff.
"If better support was available, less women would face the disappointment of not being able to breastfeed. However, not all women do successfully breastfeed their baby and it is critical, as this study points out, that midwives are also able to support women positively when this is the case.
"Women should not feel guilty about not breastfeeding and should be helped to feed their baby in a way which encourages close contact and mother/baby interaction."