Wednesday August 20 2014
Breastfeeding has many health benefits
Mothers who plan, but are unable, to breastfeed their babies are more likely to suffer from postnatal depression, report BBC News and The Independent.
A study of 14,000 women in England found that those who planned to breastfeed but had not managed to were two-and-a-half times more likely to develop postnatal depression, compared to women who had no intention of breastfeeding.
Around 1 in 10 women develop postnatal depression, which is not the same as the “baby blues”, but a serious illness that can affect a mother’s ability to bond with her baby. It can also affect the baby’s longer-term development.
It can develop within the first six weeks of giving birth, but is often not apparent until around six months. It’s important to get professional help if you think you may be suffering from this illness.
The study had several limitations. For example, both antenatal and postnatal depression were self-reported rather than clinically diagnosed, which may make the results less reliable.
Due to the nature of the study’s design, it cannot prove that not breastfeeding raises the risk of postnatal depression. However, it highlights the need to support new mothers who want to breastfeed but are unable to do so.
Where did the story come from?
The study was carried out by researchers from the University of Seville, University of Cambridge, University of Essex and University of London. It was funded by the UK’s Economic and Social Research Council. The study was published in the peer-reviewed Journal of Maternal and Child Health.
The Mail Online’s claim that “choosing not to” breastfeed doubles the risk of postnatal depression was misleading and oversimplified the study’s results.
The media did not point out that the majority of results were compared to women who did not want to breastfeed (and, subsequently, didn’t). For example, the doubled risk of postnatal depression for women who wanted to breastfeed but couldn’t was compared to women who did not want to breastfeed and didn’t. Most of the associations reported by the media were only significant at eight weeks after birth, and not significant beyond that.
As the authors point out, their results on the association between maternal depression and breastfeeding were very mixed. The link between not breastfeeding and postnatal depression seems to depend on whether or not a woman planned to breastfeed in the first place, as well as her mental health during pregnancy.
What kind of research was this?
Researchers used data from a longitudinal survey of about 14,000 children born in the early 1990s, conducted by the University of Bristol, which looked at child health and development.
The authors point out that about 3% of women experience postpartum depression (PPD) within 14 weeks of giving birth. Overall, as many as 19% of women have a depressive episode during pregnancy or the three months after birth. However, they say the effects of breastfeeding on the risk of PPD is not well understood.
The researchers aimed to examine how breastfeeding affects a mother’s mental health and, in particular, if the relationship between breastfeeding and maternal mental health is mediated by whether or not the mother intended to breastfeed.
The relationship between breastfeeding and the risk of PPD, they say, may be driven by biological factors, such as the difference in hormone levels between breast- and formula-feeding mothers. However, it may also be affected by feelings of success or failure over breastfeeding.
As this was a cohort study, it can only show an association, it cannot prove that not breastfeeding causes PPD.
What did the research involve?
The researchers used a sample of just over 14,000 women, who were recruited into the survey by doctors, when they first reported their pregnancy. Data for the study was collected by questionnaires administered to both parents at four points during pregnancy, and at several stages following birth.
Researchers used a validated measure of depression called the Edinburgh Postnatal Depression Scale (EPDS), which is designed to screen for PPD. This was conducted when women were 18 and 32 weeks pregnant. They conducted it again at 8 weeks, and 8, 18 and 33 months after the birth.
The EPDS consists of 10 questions, each with four possible answers, to describe the severity of depressive symptoms. Total scores range from 0 to 30. Following guidelines, the researchers used a score of more than 14 to indicate depression during the antenatal period and more than 12 to indicate depression after birth.
Mothers were asked during pregnancy how they intended to feed their babies for the first four weeks. Following their child’s birth, they were asked at several points how they were actually feeding, and the ages at which infant formula and solid foods were introduced.
Researchers included in their analysis how long mothers had breastfed for and how long they had breastfed exclusively.
They identified four groups of women:
- mothers who had not planned to breastfeed, and who did not breastfeed (reference group)
- mothers who had not planned to breastfeed, but who did actually breastfeed
- mothers who had planned to breastfeed, but who did not actually breastfeed
- mothers who had planned to breastfeed, and who did actually breastfeed
Using statistical methods, they presented several models of the relationship between breastfeeding and depression, controlling for different factors such as the child’s sex, parents' education and information on the pregnancy and birth. The most reliable model takes account of as many factors as possible, including the mother’s physical and mental health, whether she was depressed in pregnancy, the quality of her personal relationships and the experience of stressful life events.
After conducting this analysis for the whole sample, they split the sample into mothers who were and who were not depressed during pregnancy; for each group, they examined the differences in outcomes between women who had planned to breastfeed, and women who had not.
What were the basic results?
Researchers found that 7% of women suffered depression at 18 weeks of pregnancy and 8% at 32 weeks. 9-12% of new mothers suffered from PPD.
Breastfeeding was initiated by 80% of mothers and 74% breastfed for one week or more. By four weeks, 56% of mothers were breastfeeding at all and 43% were breastfeeding exclusively.
Researchers found that for the sample as a whole, there was little evidence of a relationship between breastfeeding and the risk of PPD. After adjusting for all of the factors, it was found that women who exclusively breastfed for 4 weeks or more were 19% less likely to have PPD 8 weeks after giving birth (odds ratio [OR] 0.81, 95% confidence interval [CI] 0.68 to 0.97). This was not significant at 8, 18 or 33 months.
However, they then calculated the results according to whether mothers had been depressed during pregnancy, and whether they had planned to breastfeed their babies.
In mothers without any depressive symptoms during pregnancy, they found that the lowest risk of PPD by 8 weeks was among women who had planned to breastfeed and did so. For example, compared to women who did not plan to breastfeed and didn’t, women who exclusively breastfed for 2 weeks or more were 42% less likely to develop PPD by 8 weeks (OR 0.58, 95% CI 0.35 to 0.96).
The highest risk was found among women who had planned to breastfeed, but had not initiated breastfeeding. They were two-and-a-half times more likely to develop PPD by 8 weeks compared to women who did not plan to breastfeed and didn’t (OR 2.55, 95% CI 1.34 to 4.84).
For women who had shown signs of depression during pregnancy, there was no difference in risk of PPD for women who had planned to breastfeed but couldn’t. The only statistically significant result was for those women who had not planned to breastfeed, but did exclusively for four weeks. Their risk of PPD was reduced by 58% compared to women who had not planned to breastfeed and didn’t (OR 0.42, 95% CI 0.20 to 0.90).
There was no significant difference in risk of PPD between any of the planned or not planned breastfeeding groups at 8, 21 or 33 months.
How did the researchers interpret the results?
The authors say that the effects of breastfeeding on the risk of maternal depression is dependent on breastfeeding intentions during pregnancy and by mothers’ mental health.
“Our results underline the importance of providing expert breastfeeding support to women who want to breastfeed, but also of providing compassionate support for women who had intended to breastfeed, but who find themselves unable to,” they argue.
This is a useful study but, as the authors point out, it does have some limitations. Both antenatal and postnatal depression were self-reported rather than clinically diagnosed, which may make the results less reliable.
Also, the fact that the study consisted of parents who had voluntarily entered the study may also lead to bias. It’s worth noting that 95% of the women were white, so the results may not be generalisable to mothers from ethnic minorities.
Finally, although the researchers controlled for many possible confounders, there is the possibility that some unmeasured factor may have influenced results, such as a mother’s personality or IQ.
Many mothers who wish to breastfeed may find it difficult to do so for a range of reasons, but professional support can help. Postnatal depression is serious, but treatment is available.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.