A study of 10,000 British women found the lowest risk of postnatal depression was among women who planned to breastfeed and were successful.
But the risk of depression was highest in women who wanted to breastfeed their babies but didn't. They were twice as likely to experience depression in the following weeks and months as the mothers who always planned to use formula milk.
Well-established benefits to babies
Dr Maria Iacovou, of the University’s Department of Sociology, said: "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.
"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’ development.
"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."
About 13% of women develop postnatal depression in the first 14 weeks after giving birth and up to 1 in 5 will also experience it in pregnancy, the researchers added.
The study followed almost 14,000 women who gave birth in Bristol in the early 1990s. They were tested for depression using a validated method when their babies were 8 weeks, 8 months, 21 months and 33 months old. They were also assessed twice during pregnancy.
Almost three-quarters of mothers initiated breastfeeding in 2012/13, but by the time of the 6-8 week check, only 47% of babies were being breastfed, according to figures from the Department of Health. This is one of the lowest rates of breastfeeding in Europe.
Commenting on the findings, chief executive of the Royal College of Midwives, Cathy Warwick, said: "It is vital women receive high-quality support immediately after the baby is born and throughout the postnatal period. The Royal College of Midwives 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."