Persuasive speech: Breastfeeding

New Evidence on Breastfeeding and Postpartum Depression: The Importance of Understanding Women’s Intentions

Cristina Borra • Maria Iacovou • Almudena Sevilla

Published online: 21 August 2014

� The Author(s) 2014. This article is published with open access at Springerlink.com

Abstract This study aimed to identify the causal effect of

breastfeeding on postpartum depression (PPD), using data

on mothers from a British survey, the Avon Longitudinal

Study of Parents and Children. Multivariate linear and

logistic regressions were performed to investigate the

effects of breastfeeding on mothers’ mental health measured

at 8 weeks, 8, 21 and 32 months postpartum. The estimated

effect of breastfeeding on PPD differed according to whe-

ther women had planned to breastfeed their babies, and by

whether they had shown signs of depression during preg-

nancy. For mothers who were not depressed during preg-

nancy, the lowest risk of PPD 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. We conclude that the effect of breastfeeding on

maternal depression is extremely heterogeneous, being

mediated both by breastfeeding intentions during pregnancy

and by mothers’ mental health during pregnancy. 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.

Keywords Breastfeeding � Mental health � Edinburgh postnatal depression scale � Child development � ALSPAC

Introduction

Approximately 13 % of women experience postpartum

depression (PPD) within the 14 weeks after giving birth

[1]. If the antenatal period is also considered, as many as

19 % of women experience a depressive episode during

pregnancy or the first 3 months postpartum [2]. Post-natal

depression has an immediate impact on mothers and carries

long-term risks for mothers’ future mental health [3, 4]; it

also has significant negative effects on the cognitive, social

and physical development of their children [5, 6]. In

addition, post-natal depression involves substantial eco-

nomic costs, in terms of costs to healthcare systems [7] and

losses in productivity via maternal absenteeism from work,

premature retirement, and long-term unemployment [8].

The effect of breastfeeding on the risk of PPD is not well

understood. Several studies have demonstrated an associ-

ation between longer breastfeeding durations and a lower

prevalence of PPD [9–14]. However, other studies have

suggested the opposite, namely that breastfeeding mothers

are at increased risk of PPD [15, 16]; or found no associ-

ation [17, 18]. Of those studies which suggest beneficial

effects from breastfeeding, several have relied on small

samples, and few have controlled for potential confounders

such as socioeconomic factors (maternal education, family

income, marital status), the quality of relationships (marital

C. Borra (&) Facultad de Ciencias Económicas y Empresariales, University of

Seville, Ramón y Cajal 1, 41018 Seville, Spain

e-mail: [email protected]

M. Iacovou

Department of Sociology, University of Cambridge, Free School

Lane, Cambridge CB2 3RQ, UK

e-mail: [email protected]

M. Iacovou

ISER, University of Essex, Colchester CO4 3SQ, UK

A. Sevilla

Queen Mary University of London, Mile End Road,

London E1 4NS, UK

e-mail: [email protected]

123

Matern Child Health J (2015) 19:897–907

DOI 10.1007/s10995-014-1591-z

stability, social networks), and stressful life events [19, 20].

Thus, it has been extremely difficult to identify whether the

observed relationships are causal, as opposed to arising

because breastfeeding is more likely to be practiced by

mothers whose characteristics are themselves associated

with a lower risk of depression [21–23]. Additionally, as Ip

et al. [24] have pointed out, most existing studies have not

controlled for pre-existing mental health conditions.

Thus, the extent to which breastfeeding influences

mental health, as opposed to mental health driving the

incidence and duration of breastfeeding, has not been clear.

The aim of the current study is to examine explicitly

whether breastfeeding affects maternal mental health out-

comes. Specifically, we examine the hypothesis that the

relationship between breastfeeding and maternal mental

health is mediated by the mother’s intention to breastfeed.

The relationship between breastfeeding and maternal

mental health may be driven by biological factors, such as

differences in hormone levels between breast- and formula-

feeding mothers [25]; if maternal mental health is also

affected by mothers’ feelings of success or failure in

relation to their original plans and aspirations, we may

expect the intention to breastfeed to play a crucial role.

Data and Methods

Data and Key Variables

This research is based on data from the Avon Longitudinal

Survey of Parents and Children (ALSPAC), a survey of

around 14,000 children born in the Bristol area of England

in the early 1990s [26]. Mothers were recruited into the

survey by doctors, at the point when they first reported their

pregnancy. Data were collected by questionnaires admin-

istered to both parents at four points during pregnancy and

at several stages following birth.

Details of all data collected in the ALSPAC survey are

available on the study website through a fully searchable

data dictionary [27]. Our study obtained ethical approval

from the ALSPAC Law and Ethics Committee and the

Local Research Ethics Committees.

We used a sample of mothers whose children form the

‘‘core sample’’ of ALSPAC. This sample consists of 14,541

pregnancies which resulted in 14,676 known foetuses;

there were 14,062 live births, and 13,988 babies surviving

to 1 year. We employed a maximizing strategy with

respect to sample size, using as many observations as

possible to analyse each outcome-effect dyad. Sample sizes

thus vary slightly between regressions. The experiences of

mothers and babies following pre-term births, or separation

due to NICU care, may differ from the experiences of other

mothers and babies. We do not exclude these mother/baby

pairs from our sample, but have checked that our results do

not change if they are excluded; these results are available

from the authors on request.

As a measure of depression, the Edinburgh Postnatal

Depression Scale (EPDS) was used. The EPDS, designed

by Cox et al. [28] to screen for PPD, was collected during

pregnancy at 18 and 32 weeks’ gestation, and post-natally

at 8 weeks, and 8, 18, and 33 months. The EPDS is the

most frequently used screening questionnaire for PPD; the

EPDS is sensitive to changes in depression over time, and

has been demonstrated to be a valid and reliable tool for the

measurement of both postpartum and antenatal depression

[29, 30]. The instrument consists of 10 questions, each with

four possible answers describing symptoms of increasing

severity or duration; aggregate scores on the EPDS range

from 0 to 30. The authors of the EPDS have suggested that

women should be referred to a mental health specialist if

they score 13 or higher during the post-partum period [31]

and 15 or more during pregnancy [32]. Therefore, we

constructed indicators of depressive symptomatology,

defined as EPDS [14 in pre-natal assessments and EPDS [12 in postpartum assessments.

Mothers were asked during pregnancy how they intended to

feed their babies for the first 4 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. Using this information, we computed seven

binary indicators: (1) initiation (putting the baby to the breast

at least once); (2–4) any breastfeeding for at least 1, 2 and

4 weeks respectively; and (5–7) exclusive breastfeeding for at

least 1, 2 and 4 weeks respectively. We also computed two

continuous indicators: total duration of breastfeeding and total

duration of exclusive breastfeeding; results for these contin-

uous indicators are similar to results obtained using the binary

indicators, and are available from the authors on request.

Analysis

We estimate multivariate logistic regressions, presenting

odds ratios and 95 % confidence intervals. All hypotheses

are tested using two-tailed p values \0.05. We present estimates from three specifications. Model A

controls only for the child’s sex and parental education.

Model B additionally controls for other socio-demographic

variables, and information on pregnancy and birth. Finally,

Model C includes information on the mother’s physical and

mental health, including antenatal EPDS assessments,

together with factors relating to the quality of interpersonal

relationships and stressful life events (see Table 6 in the

Appendix for precise definitions of these variables). Thus,

Model A provides a first approximation to the associations of

interest, Model B estimates these relationships net of a range

of potential confounders, while Model C aims to estimate

898 Matern Child Health J (2015) 19:897–907

123

causal relationships as accurately as possible by eliminating

potential reverse causality arising from the fact that previ-

ously depression-prone mothers may be less likely to decide

to breastfeed, or to breastfeed for shorter durations.

After conducting this analysis for the whole sample, we

split the sample into mothers who were, and who were not,

depressed during pregnancy; for each group, we examine

differences in outcomes between women who had planned

to breastfeed, and women who had not.

Results

Study Variables

Descriptive statistics for variables of interest are shown in

Table 1. The prevalence of antenatal depression, using a

cut-off of EPDS [14, is 7 % at 18 weeks’ pregnancy and 8 % at 32 weeks, similar to rates reported in previous

studies [33]. Rates of PPD were between 9 and 12 %, also

similar to results from former analyses [34].

80 % of mothers in this sample initiated breastfeeding

and 74 % breastfed for 1 week or more. By 4 weeks only

56 % of mothers were breastfeeding at all and only 43 %

were breastfeeding exclusively. The percentages of women

feeding for the different durations considered are shown in

Table 1; mean durations for breastfeeding and exclusive

breastfeeding are also shown.

Table 2 shows the raw relationships between postnatal

depressive symptomatology, and (a) prenatal depression,

and (b) different measures of breastfeeding duration. A

significant degree of correlation is present between post-

natal and antenatal EPDS scores; a clear negative rela-

tionship also exists between symptoms of maternal

depression measured at 8 weeks, and breastfeeding dura-

tion. The association between depression and breastfeeding

is always negative, but generally statistically insignificant,

at 8, 21 and 33 months.

Sample Characteristics

Socio-demographic characteristics for sample members are

presented in Table 7 in the Appendix. The mean age of

participants was 28.3 years (SD = 4.8). 95 % of the women

were white, 86 % were married, 13 % had university

degrees, while a further 22 % had high school qualifications

at age 18 (‘‘A’’ levels); and 74 % owned the house in which

they lived. In relation to pregnancy and birth, 64 % felt

usually well, 55 % percent were working while pregnant,

45 % were primiparous, and only 9 % delivered via Cesar-

ean section. The average gestational age was 39.5 weeks

(SD = 1.8). 48 % of mothers and 37 % of fathers had

themselves been breastfed as babies. 28 % of the pregnan-

cies were unplanned; 15 % of mothers had lived through

their own parents’ divorce before their eighteenth birthday.

Table 3 presents the results of logistic regressions esti-

mating the effect of breastfeeding on PPD.

As explained earlier, three models are estimated: Model

A controls only for the child’s sex and parental education;

Model B controls in addition for a wide range of socio-

economic and demographic factors, plus information on

pregnancy and birth; and Model C also controls for

mother’s health (including mental health) in pregnancy,

relationship quality and stressful life events.

We consider four different outcomes: EPDS [12 mea- sured at 8 weeks, 8, 21 and 33 months postpartum. For

each model/outcome dyad, the model is estimated seven

times, for seven different measures of breastfeeding (ini-

tiation; any breastfeeding for at least 1, 2 and 4 weeks; and

exclusive breastfeeding for at least 1, 2 and 4 weeks).

Thus, each coefficient in Table 3 comes from a separate

regression.

At 8 weeks postpartum, we observe a pronounced

relationship between breastfeeding and PPD, under both

Table 1 Descriptive statistics for variables of interest

N mean s.d.

Maternal mental health during pregnancy

At risk of antenatal depression, 18 weeks

(EPDS [14) 10,904 7 % (0.3)

At risk of antenatal depression, 32 weeks

(EPDS [14) 11,305 8 % (0.3)

Maternal mental health post-partum

At risk of postpartum depression, 8 weeks

(EPDS [12) 10,756 10 % (0.3)

At risk of postpartum depression, 8 months

(EPDS [12) 10,345 8 % (0.3)

At risk of postpartum depression,

21 months (EPDS [12) 9,605 10 % (0.3)

At risk of postpartum depression,

33 months (EPDS [12) 8,985 12 % (0.3)

Breastfeeding

Mother intended to breastfeed 11,547 65 % (0.5)

Initiated breastfeeding 11,012 80 % (0.4)

Breastfed for 1 week 10,668 74 % (0.4)

Breastfed for 2 weeks 10,680 68 % (0.5)

Breastfed for 4 weeks 10,972 56 % (0.5)

Duration of any breastfeeding (months) 8,317 5.17 (4.7)

Exclusively breastfed for 1 week 10,668 64 % (0.5)

Exclusively breastfed for 2 weeks 10,680 60 % (0.5)

Exclusively breastfed for 4 weeks 10,972 43 % (0.5)

Duration of exclusive breastfeeding

(months)

8,726 1.31 (1.2)

Figures in the middle column are means in the case of continuous

variables, and percentages of the sample in the case of dichotomous

variables

Matern Child Health J (2015) 19:897–907 899

123

Models A and B. The odds ratios for these models indicate

that longer durations of breastfeeding are associated with

larger reductions in the risk of PPD, and exclusive

breastfeeding is associated with a larger reduction than any

breastfeeding. However, under Model C, when we control

for mothers’ health during pregnancy, these effects largely

disappear; the only significant relationship which remains

comes from exclusive breastfeeding for 4 weeks or longer

(OR 0.81, 95 % CI 0.68, 0.97).

The relationship between breastfeeding and PPD is also

weaker, the later the EPDS score is assessed; at 8 months

postpartum and thereafter, most of the estimated coeffi-

cients are not significantly different from zero (indeed, a

few of the results are counter-intuitive, suggesting that

breastfeeding may be positively related to an increased risk

of depression measured at 33 months postpartum).

Thus, for the sample as a whole, our results demonstrate little

evidence for a causal relationship between breastfeeding and the

risk of PPD. In the next section, we investigate the possibility

that the relationship between breastfeeding and depression

varies according to two factors: whether mothers were assessed

as at risk of depression during pregnancy, and whether they had

been planning to breastfeed their babies. We show that the

relationship between breastfeeding and depression is indeed

highly heterogeneous, and that this fact explains why little effect

is found when considering women as a homogeneous group.

Heterogeneous Effects by Mental Health During

Pregnancy and Breastfeeding Intention

We re-estimated Model C separately for mothers who

were, and who were not, depressed during pregnancy (in

terms of having a score EPDS [14 at least once during pregnancy). As before, we estimated regressions separately

for each time at which postnatal depression was assessed

(8 weeks, and 8, 21 and 33 months postpartum); for each

of these time periods, we estimated seven models, one for

each discrete measure of breastfeeding. However, instead

of simply controlling for whether or not mothers breastfed

for the relevant duration, we identify four groups of

women, by whether they had planned to breastfeed, and

whether they had actually breastfed for the relevant dura-

tion. These four groups are:

• 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

Each regression thus generates three coefficients of

interest; these coefficients are expressed as odds ratios,

relative to the reference group.

Table 4 presents results for mothers without prenatal

depression symptoms. Column (2) displays odds ratios and

confidence intervals for mothers who did not plan to

breastfeed, but who did actually breastfeed; column (3)

indicates whether these mothers are significantly different

from the mothers in the reference group.

Column (4) presents odds ratios for mothers who planned

to breastfeed but who did not breastfeed for the relevant

duration; Column (5) present odds ratios for mothers who

Table 2 Raw correlations between study variables

Postpartum EPDS scores

Postnatal EPDS [12 Postnatal EPDS [12 Postnatal EPDS [12 Postnatal EPDS [12 at 8 weeks at 8 months at 21 months at 33 months

Maternal mental health during pregnancy

Antenatal EPDS [14 at 18 weeks 0.279*** 0.220*** 0.216*** 0.207*** Antenatal EPDS [14 at 32 weeks 0.350*** 0.309*** 0.288*** 0.271*** Breastfeeding measures

Initiated breastfeeding -0.034** -0.027* -0.018 -0.018

Breastfed for 1 week or more -0.037** -0.021 -0.019 -0.015

Breastfed for 2 weeks or more -0.038** -0.023 -0.015 -0.010

Breastfed for 4 weeks or more -0.037** -0.011 -0.005 -0.005

Duration of any breastfeeding -0.044*** -0.021 -0.020 -0.009

Exclusively breastfed for 1 week or more -0.041*** -0.019 -0.023 -0.022

Exclusively breastfed for 2 weeks or more -0.040*** -0.033** -0.018 -0.026*

Exclusively breastfed for 4 weeks or more -0.052*** -0.021 -0.016 -0.013

Duration of exclusive breastfeeding -0.036** -0.025 -0.021 -0.014

P values are indicated by asterisks, with * P \ 0.05, ** P \ 0.01, *** P \ 0.001

900 Matern Child Health J (2015) 19:897–907

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planned to breastfeed, and who did breastfeed for the rele-

vant duration. Column (6) indicates whether the odds ratios

in Column (4) and (5) are significantly different from each

other. Thus, the test results in Column (3) indicate whether

breastfeeding makes a difference in the case of women who

did not originally plan to breastfeed, while the tests in Col-

umn (6) indicate whether breastfeeding makes a difference in

the case of mothers who had planned to breastfeed.

The strongest result from Table 4 is that breastfeeding is

strongly associated with a lower risk of depression at

Table 3 Results from logistic regressions: effects of breastfeeding on postpartum depression

Model A

Adjusted OR

[95 % CI]

Model B

Adjusted OR

[95 % CI]

Model C

Adjusted OR

[95 % CI]

Dependent variable: EPDS [12 at 8 weeks Breastfeeding initiated 0.87 [0.74,1.03] 1.06 [0.88,1.27] 1.1 [0.89,1.37]

Any b/f, 1 week ? 0.8 [0.69,0.93]** 0.95 [0.80,1.13] 1.08 [0.88,1.33]

Any b/f, 2 weeks ? 0.83 [0.71,0.96]* 0.93 [0.78,1.09] 0.98 [0.81,1.19]

Any b/f, 4 weeks ? 0.77 [0.67,0.89]*** 0.81 [0.70,0.95]** 0.88 [0.74,1.06]

Exclusive b/f, 1 week ? 0.8 [0.70,0.92]** 0.91 [0.78,1.06] 0.99 [0.82,1.19]

Exclusive b/f, 2 weeks ? 0.78 [0.68,0.90]*** 0.85 [0.73,0.99]* 0.89 [0.74,1.06]

Exclusive b/f, 4 weeks ? 0.73 [0.64,0.85]*** 0.75 [0.64,0.88]*** 0.81 [0.68,0.97]*

N 10,509–10,546 10,393–10,428 9,722–9,757

Dependent variable: EPDS [12 at 8 months Breastfeeding initiated 0.86 [0.72,1.03] 1.01 [0.83,1.23] 0.99 [0.79,1.24]

Any b/f, 1 week ? 0.9 [0.76,1.07] 1.04 [0.86,1.25] 1.15 [0.93,1.43]

Any b/f, 2 weeks ? 0.88 [0.75,1.03] 0.98 [0.82,1.17] 1.02 [0.84,1.25]

Any b/f, 4 weeks ? 0.89 [0.76,1.04] 0.95 [0.81,1.13] 1.05 [0.87,1.28]

Exclusive b/f, 1 week ? 0.92 [0.79,1.07] 1.02 [0.86,1.21] 1.12 [0.92,1.36]

Exclusive b/f, 2 weeks ? 0.83 [0.71,0.97]* 0.9 [0.76,1.06] 0.93 [0.77,1.12]

Exclusive b/f, 4 weeks ? 0.86 [0.74,1.00] 0.9 [0.76,1.06] 1.02 [0.84,1.23]

N 10,080–10,116 9,258–9,999 9,354–9,388

Dependent variable: EPDS [12 at 21 months Breastfeeding initiated 0.93 [0.78,1.11] 1.08 [0.89,1.32] 1.09 [0.87,1.37]

Any b/f, 1 week ? 0.97 [0.82,1.15] 1.14 [0.94,1.38] 1.26 [1.02,1.56]*

Any b/f, 2 weeks ? 1 [0.86,1.18] 1.11 [0.93,1.33] 1.19 [0.97,1.46]

Any b/f, 4 weeks ? 0.99 [0.85,1.14] 1.03 [0.87,1.21] 1.15 [0.95,1.38]

Exclusive b/f, 1 week ? 0.93 [0.80,1.08] 1.04 [0.88,1.23] 1.19 [0.98,1.44]

Exclusive b/f, 2 weeks ? 0.96 [0.82,1.11] 1.03 [0.87,1.21] 1.11 [0.92,1.33]

Exclusive b/f, 4 weeks ? 0.9 [0.77,1.04] 0.92 [0.79,1.08] 1.06 [0.88,1.27]

N 9,370–9,406 9,258–9,929 8,704–8,737

Dependent variable: EPDS [12 at 33 months Breastfeeding initiated 1.04 [0.88,1.24] 1.22 [1.01,1.48]* 1.22 [0.98,1.51]

Any b/f, 1 week ? 1.01 [0.86,1.18] 1.16 [0.97,1.39] 1.27 [1.04,1.55]*

Any b/f, 2 weeks ? 1.02 [0.87,1.18] 1.13 [0.95,1.33] 1.19 [0.99,1.44]

Any b/f, 4 weeks ? 1.01 [0.88,1.16] 1.07 [0.92,1.25] 1.17 [0.98,1.39]

Exclusive b/f, 1 week ? 0.92 [0.80,1.06] 1.01 [0.86,1.18] 1.09 [0.92,1.30]

Exclusive b/f, 2 weeks ? 0.9 [0.78,1.03] 0.96 [0.82,1.11] 0.99 [0.84,1.18]

Exclusive b/f, 4 weeks ? 0.95 [0.83,1.09] 0.98 [0.85,1.14] 1.1 [0.93,1.29]

N 8,704–8,805 8,676–8,706 8,172–8,202

Coefficients are expressed as odds ratios and 95 % confidence intervals. Each estimated coefficient comes from a different regression. Model A

controls for the child’s sex and parental education. Model B additionally controls for pregnancy and birth information; child characteristics at

birth; demographic and socio-economic variables; and breastfeeding attitudes. Model C also controls for mother’s health in pregnancy, inter-

personal relationships, and stressful life events (see Table 6 in the Appendix). Sample sizes vary slightly between regressions; the range of N is

given in each panel

P values are indicated by asterisks, with * P \ 0.05, ** P \ 0.01, *** P \ 0.001

Matern Child Health J (2015) 19:897–907 901

123

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b /f

, 2

w e e k s

? –

0 .8

7 [0

.5 6 ,

1 .3

6 ]

1 .4

7 [0

.9 7 ,

2 .2

4 ]

0 .9

2 [0

.5 2 ,

1 .6

3 ]

A n y

b /f

, 4

w e e k s

? –

0 .8

0 [0

.4 7 ,

1 .3

4 ]

1 .3

2 [0

.9 5 ,

1 .8

5 ]

1 .1

3 [0

.6 2 ,

2 .0

3 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .0

0 [0

.6 4 ,

1 .5

5 ]

1 .3

9 [0

.9 4 ,

2 .0

6 ]

0 .9

5 [0

.5 5 ,

1 .6

6 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

0 .7

7 [0

.4 7 ,

1 .2

6 ]

1 .5

9 [1

.1 3 ,

2 .2

4 ]

0 .9

3 [0

.5 3 ,

1 .6

6 ]

E x c lu

si v e

b /f

, 4

w e e k s

? –

0 .6

6 [0

.3 3 ,

1 .3

1 ]

1 .3

0 [0

.9 7 ,

1 .7

3 ]

1 .4

9 [0

.7 2 ,

3 .0

8 ]

E P

D S

[ 1 2

a t

2 1

m o n th

s (N

= 7 ,7

5 1 – 7 ,7

8 7 )

B re

a st

fe e d in

g in

it ia

te d

– 1 .1

6 [0

.8 2 ,

1 .6

4 ]

1 .6

7 [0

.8 0 ,

3 .4

8 ]

0 .5

6 [0

.2 6 ,

1 .2

1 ]

A n y

b /f

, 1

w e e k

? –

1 .4

4 [1

.0 0 ,

2 .0

8 ]

* 0 .8

7 [0

.4 9 ,

1 .5

5 ]

0 .9

5 [0

.5 0 ,

1 .8

1 ]

A n y

b /f

, 2

w e e k s

? –

1 .6

2 [1

.1 2 ,

2 .3

6 ]

* 1 .1

8 [0

.7 7 ,

1 .8

0 ]

0 .6

4 [0

.3 8 ,

1 .0

8 ]

A n y

b /f

, 4

w e e k s

? –

1 .6

1 [1

.0 7 ,

2 .4

3 ]

* 1 .1

6 [0

.8 4 ,

1 .5

9 ]

0 .6

1 [0

.3 8 ,

1 .0

0 ]

*

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .4

9 [1

.0 2 ,

2 .1

8 ]

* 1 .0

0 [0

.6 8 ,

1 .4

8 ]

0 .8

0 [0

.4 8 ,

1 .3

3 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

1 .3

4 [0

.9 0 ,

2 .0

1 ]

1 .0

8 [0

.7 7 ,

1 .5

2 ]

0 .7

9 [0

.4 8 ,

1 .2

9 ]

E x c lu

si v e

b /f

, 4

w e e k s

? –

1 .3

2 [0

.7 9 ,

2 .2

0 ]

1 .0

7 [0

.8 2 ,

1 .4

0 ]

0 .7

7 [0

.4 4 ,

1 .3

4 ]

E P

D S

[ 1 2

a t

3 3

m o n th

s (N

= 7 ,3

0 0 – 7 ,3

3 0 )

B re

a st

fe e d in

g in

it ia

te d

– 1 .1

2 [0

.8 1 ,

1 .5

5 ]

1 .3

2 [0

.6 3 ,

2 .7

5 ]

0 .9

2 [0

.4 2 ,

1 .9

8 ]

A n y

b /f

, 1

w e e k

? –

1 .2

4 [0

.8 9 ,

1 .7

4 ]

1 .2

7 [0

.7 9 ,

2 .0

6 ]

0 .8

7 [0

.5 0 ,

1 .5

0 ]

A n y

b /f

, 2

w e e k s

? –

1 .4

5 [1

.0 2 ,

2 .0

5 ]

* 1 .6

0 [1

.1 1 ,

2 .3

2 ]

0 .6

2 [0

.3 9 ,

0 .9

9 ]

* *

A n y

b /f

, 4

w e e k s

? –

1 .2

3 [0

.8 3 ,

1 .8

2 ]

1 .2

8 [0

.9 6 ,

1 .7

1 ]

0 .8

7 [0

.5 5 ,

1 .3

8 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .3

1 [0

.9 1 ,

1 .8

7 ]

1 .5

4 [1

.1 1 ,

2 .1

4 ]

0 .6

6 [0

.4 2 ,

1 .0

4 ]

* *

E x c lu

si v e

b /f

, 2

w e e k s

? –

1 .1

5 [0

.7 8 ,

1 .6

8 ]

1 .5

9 [1

.1 8 ,

2 .1

3 ]

0 .6

8 [0

.4 3 ,

1 .0

7 ]

* *

E x c lu

si v e

b /f

, 4

w e e k s

? –

1 .0

5 [0

.6 4 ,

1 .7

3 ]

1 .2

5 [0

.9 7 ,

1 .5

9 ]

1 .0

2 [0

.6 0 ,

1 .7

5 ]

E a c h

ro w

p re

se n ts

a se

t o f

th re

e c o e ffi

c ie

n ts

fr o m

th e

sa m

e re

g re

ss io

n ;

th e se

a re

e x p re

ss e d

a s

o d d s

ra ti

o s

re la

ti v e

to th

e re

fe re

n c e

g ro

u p ,

w it

h 9 5

% c o n fi

d e n c e

in te

rv a ls

. T

h e

c o e ffi

c ie

n ts

in e a c h

ro w

c o m

e fr

o m

a

d if

fe re

n t

re g re

ss io

n .

M o d e l

C is

e st

im a te

d ,

c o n tr

o ll

in g

fo r

a ll

v a ri

a b le

s in

T a b le

6 .S

a m

p le

si z e s

v a ry

sl ig

h tl

y b e tw

e e n

re g re

ss io

n s;

th e

ra n g e

o f

N is

g iv

e n

in e a c h

p a n e l

P v a lu

e s

a re

in d ic

a te

d b y

a st

e ri

sk s,

w it

h *

P \

0 .0

5 ,

* *

P \

0 .0

1 ,

* * *

P \

0 .0

0 1

902 Matern Child Health J (2015) 19:897–907

123

8 weeks postpartum, for women who had planned to

breastfeed. The odds ratios in Column 4 are all well over 1,

while the odds ratios in Column 5 are all well below 1; the

differences between the two are statistically significant at

the 1 % level or better for the first six measures of

breastfeeding, and significant at the 5 % level for the

remaining measure. The effects are smaller for later

assessment periods. At 8 and 21 months, the odds ratios in

Column 5 are lower than the odds ratios in Column 4 in

almost all cases; however, the differences are not statisti-

cally significant. At 33 months, the differences are larger

again, and are significant at the 1 % level for three of the

seven measures of breastfeeding.

Interestingly, among the group of mothers who had not

planned to breastfeed, the risk of depression was higher among

women who went on to breastfeed. These differences are

statistically significant for depression measured at 21 months,

the largest being for any breastfeeding for 2 weeks on EPDS at

21 months (OR 1.62; 95 % CI 1.12, 2.36); at 8 weeks and

33 months the coefficients are all positive, though not gen-

erally significant at the 5 % level). To test whether our results

were driven by a few mothers with very severe depressive

symptoms, we repeated the analysis excluding those mothers

with EPDS scores of 20 or more (the cut-off used in general

practitioners’ guidelines [35] ); the results were virtually the

same. We also investigated whether the effects depended on

whether the mother was primiparous or multiparous, as sug-

gested by [36]; again, the results were not affected.

Results for mothers who had been assessed as at risk of

depression during pregnancy are shown in Table 5. For this

group, results are less well defined, at least in part because of

the smaller sample size. Our findings suggest that among

women who had planned to breastfeed, breastfeeding is

associated with a lower risk of PPD (as for mothers not

depressed during pregnancy, although with a much smaller

effect). However, for previously depressed mothers, there

may also be a protective effect from breastfeeding when

mothers had not planned to breastfeed. These results should

be interpreted with caution: the only significant effect was

found on EPDS measured at 8 weeks and for at least 4 weeks’

exclusive breastfeeding (OR 0.42; 95 % CI 0.20, 0.90).

Discussion

The aim of this study was to examine whether breast-

feeding influenced the risks of postnatal depression. This

study extends previous research by using a large longitu-

dinal dataset; controlling for a large set of socioeconomic,

relational, and psychosocial confounders; measuring

maternal mood at different time points both before and

after delivery; and utilising several measures of breast-

feeding initiation, duration, and exclusivity.

We found that the effect of breastfeeding on maternal

mood differed by both maternal mental health during preg-

nancy; and whether mothers intended to breastfeed. To our

knowledge, this study is the first to document this result.

For the majority of mothers who did not show symptoms

of depression before birth, breastfeeding decreased the risk

of PPD among mothers who had intended to breastfeed, but

increased the risk of PPD among mothers who had not

intended to breastfeed.

We also found that the beneficial effects of breastfeed-

ing were strongest at 8 weeks after birth, and that the

association was weaker at 8 months and onwards. This

finding is in line with the findings of the only other lon-

gitudinal research in this area [37] which significant effects

at 6 weeks but not at 12 weeks postpartum. Our results are

nevertheless important, because of the established rela-

tionship between depression, even in the very early post-

partum period, and maternal-infant bonding [38].

Estimates for the smaller group of mothers who had

shown signs of depression during pregnancy were less

precise, but differed from the estimates for non-depressed

women in two important ways. The protective effects of

breastfeeding as planned were smaller for women who had

been depressed during pregnancy; but exclusive breast-

feeding for 4 weeks appeared to exercise a protective effect

for this group, which it did not do for the women who had

not been depressed in pregnancy.

We recognize several limitations in our analyses.

Although we employ the most commonly used measure of

depressive symptomatology, we acknowledge that includ-

ing a clinical diagnosis of antenatal and PPD would have

increased the value of our findings. Also, misclassification

bias may arise when relying on self-report methods to

assess breastfeeding outcomes. Thirdly, even though we

use a large population-based sample with low loss to fol-

low-up, sampling bias resulting from the voluntary nature

of participation in the survey could have influenced results.

For instance, we acknowledge a shortfall in the numbers of

ethnic minority mothers that may limit the generalizability

of the results. Finally, even though we control for many

more potential confounders than any other study on the

subject, there may remain some unobserved factor, for

example aspects of maternal IQ or personality, which could

affect the results.

In summary, the effect of breastfeeding on maternal

depression symptoms was found to be highly heteroge-

neous and, crucially, mediated by breastfeeding intentions

during pregnancy. Our most important finding relates to the

majority of mothers who were not depressed during preg-

nancy, and who planned to breastfeed their babies. For

these mothers, breastfeeding as planned decreased the risks

of PPD, while not being able to breastfeed as planned

increased the risks. These findings have implications for

Matern Child Health J (2015) 19:897–907 903

123

T a

b le

5 R

e su

lt s

fr o

m lo

g is

ti c

re g

re ss

io n

s: e ff

e c ts

o f

b re

a st

fe e d

in g

o n

p o

st p

a rt

u m

m e n

ta l

h e a lt

h (m

o th

e rs

a t

ri sk

o f

d e p

re ss

io n

w h

e n

p re

g n

a n

t)

D e p e n d e n t

v a ri

a b le

(1 )

D id

n ’t

p la

n to

b re

a st

fe e d ,

d id

n ’t

b re

a st

fe e d

(r e fe

re n c e

g ro

u p )

(2 )

D id

n ’t

p la

n

to b re

a st

fe e d ,

d id

a c u a ll

y b re

a st

fe e d

(3 )

D if

fe re

n c e

b e tw

e e n

c o e ff

s

(1 )

a n d

(2 )

(4 )

P la

n n e d

to

b re

a st

fe e d ,

d id

n ’t

b re

a st

fe e d

(5 )

P la

n n e d

to

b re

a st

fe e d ,

d id

b re

a st

fe e d

(6 )

D if

fe re

n c e

b e tw

e e n

c o e ff

s

(4 )

a n d

(5 )

E P

D S

[ 1 2

a t

8 w

e e k s

(N =

1 ,1

2 4 – 1 ,1

2 8 )

B re

a st

fe e d in

g in

it ia

te d

– 1 .2

4 [0

.7 9 ,1

.9 4 ]

0 .8

2 [0

.2 9 ,2

.3 4 ]

1 .1

1 [0

.3 7 ,3

.3 3 ]

A n y

b /f

, 1

w e e k

? –

1 .3

3 [0

.8 1 ,2

.1 9 ]

1 .4

5 [0

.7 4 ,2

.8 4 ]

0 .5

6 [0

.2 5 ,1

.2 4 ]

A n y

b /f

, 2

w e e k s

? –

1 .0

6 [0

.6 3 ,1

.8 0 ]

1 .7

1 [0

.9 5 ,3

.0 7 ]

0 .4

7 [0

.2 2 ,1

.0 2 ]

* *

A n y

b /f

, 4

w e e k s

? –

0 .6

9 [0

.3 7 ,1

.2 8 ]

1 .1

0 [0

.7 3 ,1

.6 7 ]

1 .1

3 [0

.5 4 ,2

.3 5 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .1

4 [0

.6 7 ,1

.9 6 ]

1 .2

9 [0

.7 7 ,2

.1 6 ]

0 .6

7 [0

.3 2 ,1

.3 7 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

1 .1

9 [0

.6 8 ,2

.0 9 ]

1 .4

6 [0

.9 1 ,2

.3 5 ]

0 .4

9 [0

.2 4 ,0

.9 9 ]

* *

E x c lu

si v e

b /f

, 4

w e e k s

? –

0 .4

2 [0

.2 0 ,0

.9 0 ]

* 1 .0

7 [0

.7 4 ,1

.5 3 ]

1 .6

5 [0

.7 1 ,3

.8 3 ]

E P

D S

[ 1 2

a t

8 m

o n th

s (N

= 1 ,0

4 2 – 1 ,0

4 7 )

B re

a st

fe e d in

g in

it ia

te d

– 0 .9

1 [0

.5 6 ,1

.4 5 ]

0 .8

5 [0

.2 8 ,2

.5 5 ]

1 .3

4 [0

.4 2 ,4

.2 8 ]

A n y

b /f

, 1

w e e k

? –

1 .0

2 [0

.6 0 ,1

.7 2 ]

1 .2

3 [0

.5 9 ,2

.5 4 ]

0 .9

1 [0

.3 8 ,2

.1 4 ]

A n y

b /f

, 2

w e e k s

? –

0 .9

8 [0

.5 6 ,1

.7 1 ]

1 .3

6 [0

.7 2 ,2

.5 7 ]

0 .8

1 [0

.3 6 ,1

.8 4 ]

A n y

b /f

, 4

w e e k s

? –

0 .9

7 [0

.5 2 ,1

.8 3 ]

1 .0

3 [0

.6 6 ,1

.6 1 ]

1 .0

9 [0

.5 1 ,2

.3 2 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .0

0 [0

.5 7 ,1

.7 6 ]

1 .0

4 [0

.5 9 ,1

.8 2 ]

1 .1

2 [0

.5 2 ,2

.4 2 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

0 .8

8 [0

.4 9 ,1

.6 0 ]

1 .0

8 [0

.6 5 ,1

.8 0 ]

1 .1

6 [0

.5 4 ,2

.4 7 ]

E x c lu

si v e

b /f

, 4

w e e k s

? –

0 .8

6 [0

.4 1 ,1

.8 0 ]

1 .0

6 [0

.7 2 ,1

.5 6 ]

1 .1

0 [0

.4 8 ,2

.5 3 ]

E P

D S

[ 1 2

a t

2 1

m o n th

s (N

= 9 4 1 – 9 4 5 )

B re

a st

fe e d in

g in

it ia

te d

– 1 .0

2 [0

.6 2 ,1

.6 9 ]

0 .3

2 [0

.0 8 ,1

.3 4 ]

3 .1

2 [0

.7 2 ,1

3 .6

4 ]

A n y

b /f

, 1

w e e k

? –

1 .0

7 [0

.6 2 ,1

.8 6 ]

0 .7

6 [0

.3 3 ,1

.7 3 ]

1 .2

6 [0

.4 9 ,3

.2 6 ]

A n y

b /f

, 2

w e e k s

? –

1 .1

1 [0

.6 3 ,1

.9 5 ]

1 .0

0 [0

.4 9 ,2

.0 1 ]

0 .9

1 [0

.3 8 ,2

.1 9 ]

A n y

b /f

, 4

w e e k s

? –

0 .8

4 [0

.4 4 ,1

.6 0 ]

0 .7

5 [0

.4 7 ,1

.2 2 ]

1 .6

8 [0

.7 6 ,3

.7 0 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

0 .8

9 [0

.4 9 ,1

.6 1 ]

0 .7

4 [0

.4 0 ,1

.3 6 ]

1 .5

0 [0

.6 6 ,3

.4 2 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

1 .0

3 [0

.5 6 ,1

.8 9 ]

0 .9

5 [0

.5 5 ,1

.6 5 ]

1 .0

1 [0

.4 6 ,2

.2 4 ]

E x c lu

si v e

b /f

, 4

w e e k s

? –

0 .6

4 [0

.3 0 ,1

.3 7 ]

0 .8

2 [0

.5 4 ,1

.2 3 ]

1 .9

3 [0

.8 2 ,4

.5 6 ]

E P

D S

[ 1 2

a t

3 3

m o n th

s (N

– 8 6 5 – 8 6 9 )

B re

a st

fe e d in

g in

it ia

te d

– 1 .2

8 [0

.7 6 ,2

.1 5 ]

1 .8

1 [0

.5 3 ,6

.1 6 ]

0 .6

1 [0

.1 7 ,2

.1 8 ]

A n y

b /f

, 1

w e e k

? –

1 .0

9 [0

.6 2 ,1

.9 2 ]

1 .1

6 [0

.5 3 ,2

.5 5 ]

1 .0

3 [0

.4 1 ,2

.5 9 ]

A n y

b /f

, 2

w e e k s

? –

1 .1

6 [0

.6 5 ,2

.0 8 ]

1 .7

0 [0

.8 8 ,3

.3 0 ]

0 .6

2 [0

.2 7 ,1

.4 5 ]

A n y

b /f

, 4

w e e k s

? –

1 .0

8 [0

.5 6 ,2

.0 8 ]

1 .2

9 [0

.8 0 ,2

.0 8 ]

0 .9

0 [0

.4 1 ,1

.9 6 ]

E x c lu

si v e

b /f

, 1

w e e k

? –

1 .0

1 [0

.5 5 ,1

.8 4 ]

1 .3

3 [0

.7 5 ,2

.3 7 ]

0 .9

2 [0

.4 2 ,2

.0 3 ]

E x c lu

si v e

b /f

, 2

w e e k s

? –

1 .1

8 [0

.6 4 ,2

.2 0 ]

1 .5

6 [0

.9 2 ,2

.6 5 ]

0 .6

5 [0

.3 0 ,1

.4 1 ]

E x c lu

si v e

b /f

, 4

w e e k s

? –

0 .9

7 [0

.4 5 ,2

.0 9 ]

1 .2

8 [0

.8 4 ,1

.9 5 ]

0 .9

7 [0

.4 1 ,2

.3 0 ]

E a c h

ro w

p re

se n ts

a se

t o f

th re

e c o e ffi

c ie

n ts

fr o m

th e

sa m

e re

g re

ss io

n ;

th e se

a re

e x p re

ss e d

a s

o d d s

ra ti

o s

re la

ti v e

to th

e re

fe re

n c e

g ro

u p ,

w it

h 9 5

% c o n fi

d e n c e

in te

rv a ls

. T

h e

c o e ffi

c ie

n ts

in e a c h

ro w

c o m

e fr

o m

a

d if

fe re

n t

re g re

ss io

n .

M o d e l

C is

e st

im a te

d ,

c o n tr

o ll

in g

fo r

a ll

v a ri

a b le

s in

T a b le

6 .S

a m

p le

si z e s

v a ry

sl ig

h tl

y b e tw

e e n

re g re

ss io

n s;

th e

ra n g e

o f

N is

g iv

e n

in e a c h

p a n e l

P v a lu

e s

a re

in d ic

a te

d b y

a st

e ri

sk s,

w it

h *

P \

0 .0

5 ,

* *

P \

0 .0

1 ,

* * *

P \

0 .0

0 1

904 Matern Child Health J (2015) 19:897–907

123

the way in which new mothers are supported; they suggest

that the provision of expert breastfeeding support may, in

addition to increasing breastfeeding rates and durations,

have the additional benefit of improving mental health

outcomes among new mothers. At the same time, it is clear

that where mothers had intended to breastfeed, not being

able to breastfeed may have deleterious consequences on

their risk of PPD, and that providing specialised support to

new mothers who had intended to breastfeed, but who for

some reason find themselves unable to breastfeed, may also

constitute a desirable health policy objective.

Acknowledgments This paper has benefited from comments pro- vided by participants at the 20th Public Economics Meeting and at the

27th Annual Conference of the European Society for Population

Economics. We acknowledge comments and support from colleagues

at ISER, particularly Emilia del Bono and Birgitta Rabe. We are

extremely grateful to all the families who took part in this study, the

midwives for their help in recruiting them, and the whole ALSPAC

team, which includes interviewers, computer and laboratory techni-

cians, clerical workers, research scientists, volunteers, managers,

receptionists and nurses. The UK Medical Research Council and the

Wellcome Trust (Grant ref: 092731) and the University of Bristol

provide core support for ALSPAC. This publication is the work of the

authors, who will all serve as guarantors for the contents of this paper.

This research was specifically funded by the UK’s Economic and

Social Research Council (ESRC) under research Grant RES-062-23-

1693 Effects of breastfeeding on children, mothers and employers.

The authors are independent from the ESRC.

Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, dis-

tribution, and reproduction in any medium, provided the original

author(s) and the source are credited.

Appendix 1

See Table 6.

Appendix 2

See Table 7.

Table 6 List of variables used in the analysis

Socio-demographic variables (at or during pregnancy)

Two dummies for housing tenure which take the value 1 if the

mother owned the house or rented the house during pregnancy

(omitted category is social housing); the number of rooms in

the house during pregnancy; neighborhood indicators with

higher values indicating a better neighbourhood; a dummy

indicating the mother’s race (white, with omitted category

nonwhite); three dummies indicating the marital status of the

mother at the time of pregnancy (married, cohabiting, single/

separated/divorced); five dummies indicating the mother’s and

father’s education level (university degree; A levels (school

qualifications obtained at age 18); O levels (school

qualifications obtained at age 16); CSE (a lower level of school

qualifications obtained at age 16) and vocational); and an

indicator variable that takes the value 1 if the mother was

working at 18 weeks of pregnancy.

Table 6 continued

Pregnancy and delivery information

A dummy that takes value 1 if the child is a female; a dummy

that takes value 1 if the child is a twin; mother’s age at birth; an

indicator variable that takes value 1 if the mother had a

cesarean section; the length of the gestation period.

Health variables

Dummy variables for different physical health levels; number of

cigarettes smoked each day measured at 32 weeks of

pregnancy; number of alcoholic beverages a day before

pregnancy; and antenatal EPDS measured at 18 and 33 months

pregnancy.

Interpersonal relationships, personality, and stressful life events

Dragona’s et al. (1992) measure of the mother’s social network

availability; Quinton and Rutter’s (1988) aggression and

affection scores for marital quality; a psychological measure of

the mother’s personality: the adult version of the Nowicki-

Strickand locus of control scale (Duke and Nowicki, 1973);

Barnett et al.’s (1983) Life Events Score; an indicator variable

that takes the value 1 if pregnancy was unplanned; an indicator

variable that takes value 1 if the mother was in local authority

care; an indicator variable that takes value 1 if she had

divorced parents by age 17; an indicator variable that takes

value 1 if the mother’s main carer died by age 17;

Table 7 Socio-demographic characteristics of study population

Units Mean (Std.

error)

Pregnancy and birth

Gestation in weeks Weeks 39.47 (1.8)

Mother’s age at birth Years 28.34 (4.8)

C-section 0/1 0.09 (0.3)

Primiparous 0/1 0.45 (0.5)

Mother works at 18 weeks 0/1 0.55 (0.5)

Cigarettes at 32 w No. 2.00 (5.1)

Previous alcohol consumption No. 2.59 (0.8)

Child characteristics at birth

Female 0/1 0.49 (0.5)

Twin 0/1 0.01 (0.1)

Birth weight grams 3,419.93 (543.9)

Head circumference inches 34.84 (1.4)

Crown-heel length inches 50.52 (2.2)

Demographic and socio-economic variables

White mother 0/1 0.95 (0.2)

Mother cohabiting 0/1 0.20 (0.4)

Mother single 0/1 0.04 (0.2)

Owner occupier 0/1 0.74 (0.4)

Matern Child Health J (2015) 19:897–907 905

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Table 7 continued

Units Mean (Std.

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Private rented 0/1 0.07 (0.3)

Number of rooms 0/1 1.59 (0.9)

Neighbourhood qual. 0/1 8.25 (2.2)

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CSE (lower-level academic quals) 0/1 0.15 (0.4)

Vocational 0/1 0.08 (0.3)

Mother’s education

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A level (academic qualifications

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O level (academic qualifications

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0/1 0.42 (0.5)

CSE (lower-level academic quals) 0/1 0.14 (0.3)

Vocational 0/1 0.10 (0.3)

Breastfeeding attitudes

Mother was breastfed 0/1 0.48 (0.5)

Father was breastfed 0/1 0.32 (0.5)

Father breastfeeding attitudes score 15.39 (2.4)

Mother’s health in pregnancy

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Mother health usually well 0/1 0.64 (0.5)

Mother health sometimes unwell 0/1 0.06 (0.2)

Mother health often unwell 0/1 0.01 (0.1)

Interpersonal relationships and stressful life events

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Mother in care 0/1 0.02 (0.2)

Mother’s parents divorced by 17 0/1 0.15 (0.4)

Mother’s parents died by 17 0/1 0.10 (0.3)

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