Factor Structure of the Japanese Version of the Edinburgh Postnatal Depression Scale in the Postpartum Period

Abstract

Background
The Edinburgh Postnatal Depression Scale (EPDS) is a widely used screening tool for postpartum depression (PPD). Although the reliability and validity of EPDS in Japanese has been confirmed and the prevalence of PPD is found to be about the same as Western countries, the factor structure of the Japanese version of EPDS has not been elucidated yet.

Methods
690 Japanese mothers completed all items of the EPDS at 1 month postpartum. We divided them randomly into two sample sets. The first sample set (n = 345) was used for exploratory factor analysis, and the second sample set was used (n = 345) for confirmatory factor analysis.

Results
The result of exploratory factor analysis indicated a three-factor model consisting of anxiety, depression and anhedonia. The results of confirmatory factor analysis suggested that the anxiety and anhedonia factors existed for EPDS in a sample of Japanese women at 1 month postpartum. The depression factor varies by the models of acceptable fit.

Conclusions
We examined EPDS scores. As a result, “anxiety” and “anhedonia” exist for EPDS among postpartum women in Japan as already reported in Western countries. Cross-cultural research is needed for future research.

Full text

Factor Structure of the Japanese Version of the
Edinburgh Postnatal Depression Scale in the Postpartum
Period
Chika Kubota
1
, Takashi Okada
1
*, Branko Aleksic
1
, Yukako Nakamura
1
, Shohko Kunimoto
1
,
Mako Morikawa
1
, Tomoko Shiino
1
, Ai Tamaji
1
, Harue Ohoka
2
, Naomi Banno
1
, Tokiko Morita
3
,
Satomi Murase
4
, Setsuko Goto
5
, Atsuko Kanai
6
, Tomoko Masuda
7
, Masahiko Ando
8
, Norio Ozaki
1
1Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan, 2Nihon Fukushi University Chuo College of Social Services, Nagoya,
Aichi, Japan, 3Meijo University Graduate School of Pharmaceutical Sciences, Nagoya, Aichi, Japan, 4Liaison Medical Marunouchi, Nagoya, Aichi, Japan, 5Nagoya
University Graduate School of Medicine, Nagoya, Aichi, Japan, 6Graduate School of Education and Human Development, Nagoya University, Nagoya, Aichi, Japan,
7Graduate School of Law, Nagoya University, Nagoya, Aichi, Japan, 8Center for Advanced Medicine and Clinical Research, Nagoya University Graduate School of
Medicine, Nagoya, Aichi, Japan
Abstract
Background:
The Edinburgh Postnatal Depression Scale (EPDS) is a widely used screening tool for postpartum depression
(PPD). Although the reliability and validity of EPDS in Japanese has been confirmed and the prevalence of PPD is found to
be about the same as Western countries, the factor structure of the Japanese version of EPDS has not been elucidated yet.
Methods:
690 Japanese mothers completed all items of the EPDS at 1 month postpartum. We divided them randomly into
two sample sets. The first sample set (n = 345) was used for exploratory factor analysis, and the second sample set was used
(n = 345) for confirmatory factor analysis.
Results:
The result of exploratory factor analysis indicated a three-factor model consisting of anxiety, depression and
anhedonia. The results of confirmatory factor analysis suggested that the anxiety and anhedonia factors existed for EPDS in
a sample of Japanese women at 1 month postpartum. The depression factor varies by the models of acceptable fit.
Conclusions:
We examined EPDS scores. As a result, ‘‘anxiety’’ and ‘‘anhedonia’’ exist for EPDS among postpartum women in
Japan as already reported in Western countries. Cross-cultural research is needed for future research.
Citation: Kubota C, Okada T, Aleksic B, Nakamura Y, Kunimoto S, et al. (2014) Factor Structure of the Japanese Version of the Edinburgh Postnatal Depression
Scale in the Postpartum Period. PLoS ONE 9(8): e103941. doi:10.1371/journal.pone.0103941
Editor: James Coyne, University of Pennsylvania, United States of America
Received December 11, 2013; Accepted July 7, 2014; Published August 4, 2014
Copyright: ß2014 Kubota et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Funding for this study was provided by research grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Ministry
of Health, Labor and Welfare of Japan; The Academic Frontier Project for Private Universities, Comparative Cognitive Science Institutes, Meijo University; the Core
Research for Evolutional Science and Technology; Intramural Research Grant (21B-2) for Neurological and Psychiatric Disorders of NCNP; and the Specific Research
Fund 2012 for East Japan Great Earthquake Revival by The New Technology Development Foundation. The funders had no role in study design, data collection
and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: Branko Aleksic and Norio Ozaki are PLOS ONE Editorial Board members. This does not alter the authors’ adherence to PLOS ONE Editorial
policies and criteria.
* Email: okada@med.nagoya-u.ac.jp
Introduction
Postpartum depression (PPD) is a type of major depressive
disorder after childbirth and is distinguished from maternity blues
in terms of onset, severity and duration of symptoms. The
prevalence of PPD is estimated at approximately 13% from meta-
analysis [1,2]. Our study shows 10.4% of women in Japan
experienced depressive symptomatology assessed by the Edin-
burgh Postnatal Depression Scale (EPDS) [3]. PPD is a major
mental health problem in women with children [4]. First, PPD
reduces maternal mental health and quality of life. 5–14% of
perinatal and postnatal women have thoughts of self-harm, and
suicides account for up to 20% of postpartum deaths [5]. Second,
PPD has a negative influence on child health and development
[6,7] because it interferes with the mother’s ability to care for a
baby and handle other daily tasks. Third, the mother-child
relationship often worsens because of PPD [8]. Severe depression
is also reported to be associated with child abuse [9].
Early detection and intervention are essential for maternal and
child health. EPDS, a 10-item self-administered questionnaire for
early detection of PPD [10], has been the most widely used
screening tool for PPD across countries and cultures. In recent
studies, the factor structure of the original English version of EPDS
has been reported as shown in Table 1 [11–18]. These results
suggest that anxiety symptoms account for a significant part of
PPD symptoms, unlike typical major depressive disorders. There
are only a few studies about the factor structure of EPDS outside
Western countries, but these studies show similar results: that
EPDS was found to contain at least two factors, a depressive factor
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and an anxiety factor in Brazil [19], China [19], and the
Netherlands [19].
The pathology of PPD has been thought to be caused by
biological and psychosocial changes with pregnancy and child-
birth. There is no direct evidence that PPD has a common
pathology across different populations, ethnicities and cultures;
however, the commonality of the prevalence of PPD [20] supports
this idea. If a common pathophysiology can be proven and this
hypothesis supported, it will become a significant step towards
understanding the common pathology of PPD. Because the cross-
cultural consistency of the factor structure of EPDS, however, has
yet not been examined, particularly outside Western countries,
more research is needed to answer the question.
In Japan, the reliability and validity of EPDS in Japanese has
been confirmed and the prevalence of PPD is found to be
comparable to the Western countries, but the factor structure of
the Japanese version of EPDS has not been elucidated. Therefore,
we examined the symptomatological structure of PPD measured
with the Japanese version of EPDS to compare with the structure
of the original English version of EPDS already reported in
Western countries.
Methods
Participants
Participants were recruited between August 2004 and October
2012. Every participant was an outpatient in a maternity ward at
one of three obstetrics and gynecology hospitals in Nagoya, Japan.
The three obstetrics hospitals were a general hospital (Nagoya
Teishin Hospital), an obstetrics and gynecology hospital (Kaseki
Hospital), and a university hospital (Nagoya University Hospital).
The eligibility criteria were as follows:
(1) attending at one of the three hospitals consecutively
(2) 20 years of age or older
(3) ability to understand the questionnaire written in Japanese.
Procedure
We explained our research design and methods to pregnant
women at maternity programs or outpatient care. In these three
hospitals, every outpatient equally receives an orientation for birth
hospitalization during the second trimester at outpatient care or
maternity program. We matched the timing of the invitation with
the timing of the orientation during the second trimester which
every patient participates. At the same time, participants received
a set of agreement documents and questionnaires. Each woman
was asked to participate in the study voluntarily and to answer all
of the questions according to the predefined schedule. If she
agreed to participate in the study, she was requested to return the
two sealed envelopes that contained the anonymous questionnaire
and the signed agreement separately. This was to guarantee
privacy. We considered a voluntarily returned envelope consent to
participate in this research.
Measurements
We assessed depressive symptoms in participants as well as their
social background (i.e. years of schooling, demographic parame-
ters). Depressive symptoms were evaluated by EPDS at about 1
month after childbirth.
EPDS is a 10-item self-report screening tool for postnatal
depression. Each item is scored on a 4-point scale ranging from 0
to 3. Total scores can range from 0 to 30. The English version of
Table 1. Factor structure of the English version of the EPDS.
First author,
Publishied year Period Country N Method Rotation Factor structure
Factor 1 Factor 2 Factor 3
Tuohy & McVey,2008 Postpartum 6.47 months U.K. 440 EEA Oblimin Non-specific depressive
symptoms:7, 8, 9, 10
Anhedonia:1, 2 Anxiety symptoms:3, 4, 5
King, 2012 Postpartum 1 week-12 months U.S.A. 169 CFA None Non-specific depressive
symptoms:7, 8, 9, 10
Anhedonia:1, 2 Anxiety symptoms:3, 4, 5
Astbury, 1994 Postpartum 8–9 months Australia 790 PCA Oblimin Depression:1, 2, 6, 7, 8, 9, 10 Anxiety:3, 4, 5 -
Matthey, 2008 Postpartum 6 weeks Australia 238 PCA Varimax Depression:1, 2, 6, 7, 8, 9, 10 Anxiety:3, 4, 5 -
Phillips, 2009 Postpartum 0–12 months Australia 309 EEA/CFA Oblimin Depression:1, 2, 6, 7, 8, 9, 10 Anxiety:3, 4, 5 -
Ross, 2003 Pregnant 36 weeks/Postpartum 6
and 16 weeks
Canada 150 PCA Varimax Depression:1, 2, 8, 9 Anxiety:3, 4, 5 Suicide 10
Jomeen, 2005 Postpartum 13.6 weeks U.K. 101 EEA/CFA Oblimin Depression:1, 2, 6, 7, 8, 9 Anxiety:3, 4, 5 Suicide 10
Swalm, 2010 Postpartum 26 weeks Australia 4706 PCA Varimax Anhedonia:1, 2 Anxiety:3, 4, 5 -
(EEA: exploratory factor analysis, CFA: confirmatory factor analysis, PCA: principal component analysis).
doi:10.1371/journal.pone.0103941.t001
Factor Structure of EPDS in Japan
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EPDS has good internal consistency (Cronbach’s alpha = 0.87)
and reliability (split half reliability = 0.88) [10].
EPDS was translated into Japanese by Okano et al. in 1996 and
confirmed that the retranslated English version was the equivalent
to the original English version [21]. The validity and reliability of
this Japanese version of EPDS were also examined against 115
non-pregnant women and 47 women at 1 month postpartum by
Okano et al [21]. It had good internal consistency (Cronbach’s
alpha = 0.78) and test–retest reliability (Spearman correlation
= 0.92) [21]. The validity was examined against a diagnosis of
major depressive disorder from the semi-structured interview-
based Research Diagnostic Criteria (RDC) [22] as external
criteria. The total score of the women who have postpartum
depression (N = 4) was higher than that of the non-depressive
postpartum women (N = 43) [21] and the cut-off point of §9
showed good sensitivity (75%) and specificity (93%) [21].
This is the standardized Japanese version and no other Japanese
version of EPDS is used in Japan. In this study, we used this
Japanese version of EPDS and the cut-off point of §9in
accordance with the previous study [21].
Data analysis
We randomly divided all participants who completed all items
of EPDS into two sample sets. The first sample set was used for
exploratory factor analysis, and the second sample set for
confirmatory factor analysis.
Exploratory Factor Analysis (EFA)
The number of factors was determined by scree plot. An EFA
with maximum-likelihood extraction was undertaken on the full
10-item EPDS. Oblique rotation using the promax rotation was
performed due to an expectation that factors would be correlated.
Confirmatory Factor Analysis (CFA)
We chose the model identified in EFA and the models reported
in the original English version of EPDS as follows:
(1) Tuohy & McVey/King; three-factor [11,15]
(2) Astbury et al. /Matthey/Phillips et al.; two-factor [13,16,17]
(3) Ross et al.; three-factor [14]
(4) Jomeen et al.; three-factor [12]
(5) Swalm et al.; two-factor [18]
(6) Model identified in the EFA; three-factor
As recommended for structural equation modeling applications
[23,24], we used the goodness-of-fit index (GFI) [25], adjusted
goodness-of-fit index (AGFI) [23], comparative fit index (CFI)
[26], and root mean square error of approximation (RMSEA)
[27]. A good fit is defined as a GFI greater than 0.95, an AGFI
greater than 0.90, a CFI greater than 0.97 and an RMSEA less
than 0.05. An acceptable fit is defined as a GFI greater than 0.90,
an AGFI greater than 0.85, a CFI greater than 0.95 and an
RMSEA less than 0.08 [25] [23] [26] [27]. Data were analyzed
using SPSS version 20.0 and Amos 19.0 (IBM Japan, Tokyo,
Japan).
Results
Characteristics of participants
812 participants agreed to participate in this study. The mean
age of the participants was 32.1 years (range: 20 to 45 years,
Standard Deviation (S.D.) 4.5 years, interquartile range (IQR) 29–
35). Average years of schooling were 14.4 years (range: 9 to 18
years, S.D. = 1.6 years, IQR 14–16). In terms of parity, 67.0% of
participants were nulliparous, 24.4% of participants were primip-
arous, 7.9% of participants had given birth two times, and 0.6% of
participants had given birth three times (range: 0 to 3 children,
S.D. = 0.7, IQR 0–1). 690 out of the 812 women completed all
items of EPDS. The non-response rate is 75 of 812 and the non-
valid response rate is 51 of 812.
EPDS scores
The median postpartum EPDS score was 3 (range: 0–22,
S.D. = 4.53, IQR 1–7). Approximately 18.4% of women scored 9–
22 and were considered at high risk of postpartum depression. The
median infant age was 31.7 days (range: 16–64, S.D. = 6.9 days,
IQR 30–34).
Factor analysis
690 participants who completed all items of EPDS were divided
randomly into two groups. The first sample set of 345 participants
was used for EFA, and the second sample set of 345 participants
was used for CFA.
EFA
The dataset was found suitable for factor analysis (the Kaiser-
Meyer-Olkin index = 0.886). The Cronbach’s alpha for the 10-
item EPDS was 0.856, indicating the test has good instrument
Table 2. Factor analysis of the Japanese version Edinburgh Postnatal Depression Scale.
Items of the EPDS Factor 1 Factor 2 Factor 3
1. I have been able to laugh and see the funny side of things. 2.034 1.055 2.075
2. I have looked forward with enjoyment to things. .026 .599 .135
3. I have blamed myself unnecessarily when things went wrong. .684 .067 .026
4. I have been anxious or worried for no good reason. .755 .023 2.072
5. I have felt scared or panicky for not very good reason. .803 2.078 2.044
6. Things have been getting on top of me. .238 .140 .141
7. I have been so unhappy that I have had difficulty sleeping. .011 .028 .741
8. I have felt sad or miserable. .352 .065 .497
9. I have been so unhappy that I have been crying. 2.112 .000 .824
10. The thought of harming myself has occurred to me. .255 2.086 .267
(N = 690, maximum-likelihood estimation, promax rotation).
doi:10.1371/journal.pone.0103941.t002
Factor Structure of EPDS in Japan
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internal reliability. The scree test indicated a three-factor solution
which accounted for 64.4% of the variance. The anhedonia,
anxiety and depression factors appeared consistent with factors
identified in our studies. A coefficient level of 0.45 or above was
chosen to indicate significant item factor loading.
The first factor, which explained 43.4% of the total variance,
included EPDS items 3, 4, 5 with factor loadings .0.45 (listed in
Table 2). Items 3, 4 and 5 were found to have the highest factor
loadings (all.0.65), consistent with previous findings that identi-
fied this factor as an ‘‘anxiety’’ subscale within EPDS. The second
factor explained 12.1% of the total variance, and included items 1
and 2 with factor loadings.0.45. Items 1 and 2 had the highest
factor loadings (.0.55), consistent with previous findings that
identified this factor as an ‘‘anhedonia’’ subscale within EPDS.
The third factor explained 8.8% of the total variance, and
included items 7, 8 and 9 with factor loadings .0.45. Items 7 and
9 had the highest factor loadings (.0.7), consistent with previous
findings that identified this factor as a ‘‘depression’’ subscale within
EPDS.
CFA
The goodness-of-fit for the data represented by GFI, AGFI, CFI
and RMSEA are shown in Table 3. In the models of Tuohy &
McVey and King, GFI and AGFI showed good fit while CFI and
RMSEA showed acceptable fit. In the models of Astbury et al. and
Matthey and Phillips et al., GFI, AGFI, CFI and RMSEA showed
unsatisfactory fit. In the model of Ross et al., GFI, AGFI, CFI and
RMSEA showed unsatisfactory fit. In the model of Jomeen et al.,
GFI, AGFI, CFI and RMSEA showed unsatisfactory fit. In the
model of Swalm et al., GFI, AGFI, CFI and RMSEA showed good
fit. In the model identified in EFA, GFI and AGFI showed good
fit. CFI and RMSEA showed acceptable fit. We therefore
concluded that there were four acceptable models: those of Tuohy
& McVey, King, Swalm et al., and as identified in EFA. We also
concluded that the models of Astbury et al., Matthey and Phillips
et al., Ross et al. and Jomeen et al. were unsatisfactory.
Correlations between factors in the models of an acceptable fit
or a good fit were as follows. In the models of Tuohy & McVey
and King, correlation between ‘‘anxiety’’ and ‘‘depression’’ was
0.84, correlation between ‘‘depression’’ and ‘‘anhedonia’’ was
0.64, and correlation between ‘‘anhedonia’’ and ‘‘anxiety’’ was
0.60. In the model of Swalm et al., correlation between
‘‘anhedonia’’ and ‘‘anxiety’’ was 0.60. In the model identified in
EFA, correlation between ‘‘anxiety’’ and ‘‘depression’’ was 0.85,
correlation between ‘‘depression’’ and ‘‘anhedonia’’ was 0.66, and
correlation between ‘‘anhedonia’’ and ‘‘anxiety’’ was 0.60.
Discussion
This is the first study demonstrating the factor structure of the
Japanese version of EPDS using a large sample of postpartum
women. The model of EFA reported by Tuohy & McVey, King
and Swalm et al., was consistent with our model in the present
study of the Japanese version of EPDS. The model consists of
common factors, an anxiety factor (items 3, 4 and 5) and an
anhedonia factor (items 1 and 2). Thus, our findings suggest that
factor structure of EPDS in Japan is basically the same as already
reported in Western countries, although there was variance
between studies on some items of EPDS.
No previous papers have reported the factor structure of the
Japanese version of EPDS, however there are some studies about
the symptoms of PPD in Japan. Tamaki et al. showed that women
with PPD have strong anxiety symptoms by the State-Trait
Anxiety Inventory Trait test [28]. Sato Y et al. revealed that the
Table 3. Goodness-of-fit of the models.
First author, Publishied year Factor structure Goodness-of-fit of the models
Factor 1 Factor 2 Factor 3 GFI AGFI CFI RMSEA
1. Tuohy & McVey, 2008/King, 2012 Non-specific depressive
symptoms:7, 8, 9, 10
Anhedonia:1, 2 Anxiety symptoms:3, 4, 5 0.965 0.934 0.958 0.065
2. Astbury, 1994/Matthey, 2008/Phillips, 2009 Depression:1, 2, 6, 7, 8, 9, 10 Anxiety:3, 4, 5 - 0.870 0.796 0.852 0.136
3. Ross, 2003 Depression:1, 2, 8, 9 Anxiety:3, 4, 5 Suicide:10 0.896 0.790 0.881 0.152
4. Jomeen, 2005 Depression:1, 2, 6, 7, 8, 9 Anxiety:3, 4, 5 Suicide:10 0.883 0.810 0.868 0.132
5. Swalm, 2010 Anhedonia:1, 2 Anxiety:3, 4, 5 - 0.992 0.970 0.995 0.05
6. Model identified in the EFA in this study Anxiety:3, 4, 5 Anhedonia:1, 2 Depression:7, 8, 9 0.954 0.902 0.962 0.092
doi:10.1371/journal.pone.0103941.t003
Factor Structure of EPDS in Japan
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prevalence of anxiety symptoms was higher than that of depressive
symptoms after childbirth [29]. These results also suggest that
anxiety symptoms are important to understand the symptomatic
character of PPD in Japan.
In the other Asian countries, there are a few studies of the factor
structure of EPDS. Small et al. analyzed the factor structure of
EPDS in Vietnam, Turkey and Philippines [30].Small et al.
pointed out that Item 6 loaded less consistently in the different
countries, however they also suggest that EPDS have two or three
factors which consists of anxiety and depression. Lau Y et al.
showed that EPDS in China consists of the three factors as
depression factor(items 6, 7, 8. 9 and 10), anxiety factor(items 3,4
and 5) and anhedonia factor(items 1 and 2) [31]. These results are
very similar to the factor structure of EPDS in Japan by our study.
The depression factor
The depression factor varies across studies. Tuohy & McVey
and King suggested items 7, 8, 9, and 10, Swalm suggested no
depression factor, and the EFA in our study showed items 7, 8, and
9. Though the best fit was the model of Swalm et al., we proposed
the EFA model because the model of Swalm excluded half of all
EPDS items. Cross-cultural studies are needed to examine whether
a common depression factor exists or not.
The anhedonia factor
All of the acceptable models show the anhedonia factor (items 1
and 2), which is reverse scoring. As reverse scoring items tend to be
in the same cluster [32], we must take into account that reverse
scoring items has been found to affect factor analysis.
The anxiety factor
The anxiety factor (items 3, 4 and 5) was shown in many
countries, such as Brazil [33,34], China [31], and the Netherlands
[19]. Considering the existence of a common anxiety factor across
different countries and cultures, the importance of anxiety
symptoms for PPD has been revealed. In fact, it is reported that
about 10% of the women experiencing postpartum depression
have anxiety symptoms [35].
The utility of the anxiety factor (items 3, 4 and 5) is discussed in
some studies as follows. Some studies have suggested that items 3,
4 and 5 can measure anxiety disorder [18,36], and other studies
suggested that items 3, 4 and 5 are enough for PPD screening [14]
[37]. Although the utility of the anxiety factor (item 3, 4 and 5)
varies by study, as mentioned before, there is some possibility of
common utility of the anxiety factor around the world.
Correlation between factors
The correlations between ‘‘anxiety’’ and ‘‘depression’’ were
found to be high in the models of acceptable fit to the data. These
results suggested that there was a very close relationship between
depression and anxiety, as previously reported [38,39], and
showed that it was important to focus on anxiety symptoms in
PPD screening and care.
Limitations
There are some types of study bias in this study. First, there is a
self-selection bias. They participated in this study voluntarily. This
also means that they pay more attention to their mental health.
Second, there are losses to follow up. Women with depression are
hard to reply the questionnaire. Third, there is a membership bias.
We cannot affirm that a standard population in Japan is shown in
these participants from three characteristic hospitals, a general
hospital, an obstetrical and gynecological hospital, and a university
hospital. The patients at the university hospital tended to have
pregnancy complications, but these participants accounted for a
small percentage of all participants (N = 42, 5.2%). Fourth, there is
a non-response bias, however the non-response rate is 75 of 812
and the non-valid response rate is 51 of 812. We consider that
these rates are not so high and the result is not affected.
Furthermore, there is a problem with this study design. We did
not ask participants for their nationality, citizenship or ethnicity.
However, Japan is considered to be highly homogenous in terms of
population, therefore we consider this problem does not affect the
result of the study.
Conclusions
We examined factor structure of the Japanese version of EPDS
in a large sample size of postpartum women in Japan. As a result,
‘‘anxiety’’, ‘‘depression’’ and ‘‘anhedonia’’ factors exist for EPDS,
as already reported in Western countries. Our findings suggest that
the factor structure of EPDS is mostly common across countries
and cultures.
Ethics Statement
This study protocol has been approved by the Ethics Committee
of the Nagoya University Graduate School of Medicine.
Author Contributions
Conceived and designed the experiments: SM SG AK TM NO. Performed
the experiments: CK YN SK MM TS AT HO NB TM. Analyzed the data:
CK MA NO. Contributed reagents/materials/analysis tools: CK YN SK
MM TS AT HO NB TM. Wrote the paper: CK TO BA YN SK MA NO.
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Factor Structure of EPDS in Japan
PLOS ONE | www.plosone.org 6 August 2014 | Volume 9 | Issue 8 | e103941