Iowa Depression and Clinical Research Center, University of Iowa
Department of Psychology, University of Iowa, USA
Department of Psychology, University of Minho, Braga, Portugal
University College Dublin, Ireland
University Department of Child Psychiatry, Centre HospitalierSaint Vincent de Paul, Paris, France
University of Zurich, Switzerland
Department of Psychiatry, University of Vienna, Austria
Department of Neurologic and Psychiatric Sciences, University of Florence, Italy
Section of Perinatal Psychiatry, Institute of Psychiatry, London, UK
University Department of Psychiatry, Centre Hospitalier Charles Perrens, Bordeaux, France
TCSPND Group*
Correspondence: Professor Michael O'Hara, Department of Psychology, E11 Seashore Hall, University of Iowa, Iowa City, IA 52242, USA. E-mail: mike-ohara{at}uiowa.edu
* TCSPND Group membership and funding detailed in Acknowledgements, p.
iv, this supplement. ![]()
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Aims To adaptthe Structured Clinical Interview for DSMIV Disorders (SCID) for assessing depression and other non-psychotic psychiatric illness perinatally and to pilotthe instrument in different centres and cultures.
Method Assessments using the adapted SCID and the Edinburgh Postnatal Depression Scale were conducted during the third trimester of pregnancy and at 6 months postpartum with 296 women from ten sites in eight countries. Point prevalence rates during pregnancy and the postnatal period and adjusted 6-month period prevalence rates were computed for caseness, depression and major depression.
Results The third trimester and 6-month point prevalence rates for perinatal depression were 6.9% and 8.0%, respectively. Postnatal 6-month period prevalence rates for perinatal depression ranged from 2.1% to 31.6% across centres and there were significant differences in these rates between centres.
Conclusions Study findings suggest that the SCID was successfully adapted for this context. Further research on determinants of differences in prevalence of depression across cultures is needed.
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Prevalence rates for postnatal depression in studies using randomly selected samples of women generally fall between 10% and 15%. A meta-analysis of 59 studies estimated the average prevalence of postnatal depression to be 13% (O'Hara & Swain, 1996). Varying rates across studies were related to the length of the postnatal period being examined and the method of assessment. Higher prevalence rates were significantly associated with longer periods of assessment and the use of self-report instruments, whereas lower rates of postnatal depression were associated with shorter periods of assessment and the use of interview-based measures (O'Hara & Swain, 1996). Although there have been numerous studies examining the frequency of postnatal depression over the years, none has directly compared rates of antenatal and postnatal depression in women from several different countries and cultural backgrounds within the same study. Conducting such a multi-site study eliminates potential confounding factors that exist when comparing rates from individual studies, such as the use of different diagnostic measures or systems, or different times of assessment. A multi-site study of postnatal depression also allows examination of the impact of potential psychosocial and cultural influences on rates of the disorder.
The Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I;
First et al, 1994) is
a semi-structured diagnostic interview which has been widely used in
psychiatric research studies (Spitzer
et al, 1992; Williams
et al, 1992a), including cross-national
epidemiological and treatment studies
(Williams et al,
1992b; Weissman
et al, 1996). The interview consists of standardised
diagnostic questions arranged in modules corresponding to each DSM-IV Axis I
disorder (American Psychiatric Association,
1994). The test-retest reliability of SCID-I generally falls
between reported values for similar instruments such as the Diagnostic
Interview Schedule and the Schedule for Affective Disorders and Schizophrenia
(Williams et al,
1992a; First et
al, 1996). In an American study using videotaped interviews,
paired raters made independent diagnoses of 75 psychiatric out-patients
(Riskind et al,
1987). The percentage agreement between raters using the SCID-I
was 82% (
=0.72) for major depressive episode and 86% (
=0.79) for
generalised anxiety disorder.
Reliability studies involving the SCID-I have also been conducted in
countries other than the USA. In a Norwegian study, interrater reliability was
excellent for the diagnoses of major depressive episode and generalised
anxiety disorder with reported
values of 0.93 and 0.95, respectively
(Skre et al, 1991).
Similarly, adequate interrater reliability using a Portuguese translation of
the SCID-I was demonstrated in a Brazilian study: for major depressive
episode,
=0.88 (Del-Ben et
al, 1996). These two studies demonstrate that the SCID-I can
be used reliably with non-American samples. High interrater reliability using
the SCID-I and similar structured interviews has also been demonstrated in
studies of women in the postnatal period
(O'Hara et al, 1990;
Wenzel et al, 2001).
In an American study examining anxiety and depressive symptoms in women
postpartum, interrater agreement for major depressive disorder using the
SCID-I was 84%,
=0.67 (Wenzel et
al, 2001).
For the Transcultural Study of Postnatal Depression (TCS-PND), the non-patient research version (SCID-I/NP) was adapted to make it more suitable for use with women in different countries and cultures. Major adaptations included deletion of modules that were not part of the project aims, the addition of new screening questions to the screening module, development of alternative psychosis and mania screening questions, insertion of a module to record the interviewee's smoking history, and replacement of the summary score sheets with a newly developed SCID recording form. Minor adaptations included rewording the original screening questions for alcohol misuse or dependence, substance misuse or dependence and obsessive-compulsive disorder, and revising the overview section to include an expanded section on psychiatric treatment history.
The final modified version used in this study for the assessment of postnatal depression, the SCID-PND, included the following modules: overview; smoking history; screening questions; major depression - current and past; dysthymia; alcohol use disorders; non-alcohol substance use disorders; panic disorder; agoraphobia; social phobia; specific phobia; obsessive-compulsive disorder; post-traumatic stress disorder; acute stress disorder; generalised anxiety disorder; somatisation disorder; anorexia nervosa; bulimia nervosa; and the mood differential module. Lifetime diagnoses of these disorders were assessed at the antenatal interview. At the postnatal interview the diagnostic assessment covered the period between the antenatal and postnatal interviews.
Transcultural Study of Postnatal Depression
The aim of the TCS-PND was to develop (or modify), translate and validate
research instruments that could be used in future studies of postnatal
depression in different countries and cultures. The instruments were chosen to
assess key aspects of the maternity experience, namely clinical diagnosis, the
psychosocial context of pregnancy and motherhood, maternal attachment style,
mother-infant interaction, the child's environment, and health service
structure, use, and its associated costs. The modified and translated research
tools were piloted to test how well they worked in a perinatal setting and in
different languages and populations. This paper reports on the development of
the SCID-PND and its piloting on women from middle or late pregnancy to about
6 months after delivery.
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Sample
Although recruitment methods varied among sites
(Asten et al, 2004,
this supplement), generally women who were in their second or third trimester
of pregnancy were approached at antenatal clinics or childbirth preparation
classes and invited to participate in a prospective study examining the
psychosocial aspects of postnatal depression. Informed consent was obtained
from those interested in participating. Antenatally 296 women were
interviewed, 261 of whom also completed a postnatal interview. Demographic
characteristics of the sample are described by Asten et al
(2004, this supplement).
Procedure
Participants were first interviewed during the third trimester of
pregnancy, on average at 34 weeks' gestation (mean 34.4 weeks, s.d.=3.5)
across the ten centres. With the exception of the Zurich group, women were
interviewed again, on average, at 26 weeks after delivery (mean 25.8 weeks,
s.d.=6.5). Women in Zurich were interviewed at 17 weeks postnatally on average
(mean 17.0 weeks, s.d.=1.6).
Other measures
The Edinburgh Postnatal Depression Scale (EPDS) is a ten-item self-report
measure developed to screen and identify women who may be experiencing
postnatal depression (Cox et al,
1987). The measure has been used widely in European studies of
postnatal depression (Holden et
al, 1989; Murray &
Carothers, 1990; Thorpe et
al, 1992; Cooper &
Murray, 1994; Augusto et
al, 1996; Wickberg &
Hwang, 1996; Appleby et
al, 1997; Guedeney & Fermanian, 1998;
Benvenuti et al, 1999)
and has been validated for use in postpartum studies of women in several other
countries (Boyce et al,
1993; Pen et al,
1994; Holt, 1995;
Areias et al, 1996).
Although the measure was developed as a screening instrument, a cut-off score
of 12/13 identifies women who are most likely to be experiencing post-partum
depression (Cox et al,
1987). The measure also has been validated as a screening measure
for depression during pregnancy (Murray
& Cox, 1990).
Training
Training in the use of the adapted SCID-I followed a standard approach that
has been used to train clinical interviewers in various epidemiological and
intervention studies over the past 20 years (O'Hara et al,
1990,
2000). Research staff from all
participating centres underwent at 2-day SCID-PND training workshop held in
Keele (UK) in March 1998. Training included an overview of administration
guidelines and descriptions of individual modules and symptom criteria for
DSM-IV Axis I disorders (American
Psychiatric Association, 1994). Workshop participants also viewed
and rated a videotaped SCID-I interview. All centres were familiar with the
user's guide for the SCID-I (First et
al, 1994). Subsequent workshops in Paris, the Tyrol,
Florence, Manchester and Dublin allotted time to discuss administration and
rating questions and issues related to the SCID-PND. No formal reliability
analysis was conducted.
Analyses
Point and adjusted 6-month period prevalence rates were examined for three
diagnostic categories of postnatal depression and anxiety and an additional
non-diagnostic category that is likely to be indicative of perinatal
depression. The broadest diagnostic category, caseness, included
participants who met DSM-IV criteria for generalised anxiety disorder, minor
depressive disorder or major depressive disorder. The second diagnostic
category, depression, included participants who met DSM-IV
criteria for minor or major depressive disorder. The third diagnostic
category, major depression, included those who met criteria for
major depressive disorder only. A final category, EPDS 13+,
included participants who scored 13 or above on the EPDS. This is the cut-off
score found to have the best specificity and sensitivity in detecting women
who might be experiencing postnatal depression
(Cox et al,
1987).
Point prevalence rates were computed for each centre for caseness,
depression, major depression and EPDS 13+ at both the antenatal and postnatal
assessment points. Period prevalence rates covering the interval between the
antenatal and postnatal interviews were computed for caseness, depression and
major depression. However, owing to significant variation in the time between
interviews among centres (range 21.4-40.4 weeks;
F(7,246)=59.15, P<0.001), period
prevalence rates were adjusted to estimated 6-month period rates and used in
2 analyses (or Fisher's exact test when necessary) to compare
rates between centres. Because the sample in Keele consisted of only five
women, data from the Keele and London centres were combined.
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View this table: [in a new window] | Table 1 Antenatal point prevalence rates |
Antenatal point prevalence rates for caseness ranged from 0% in Vienna to 23.3% in Bordeaux. The rates of caseness in Bordeaux and Porto were significantly higher than the rate in Vienna (P=0.048 and P=0.032, respectively), and the rate in Zurich was significantly lower than rates in Porto (P=0.004), Dublin (P=0.037) and Bordeaux (P=0.011). Antenatal point prevalence rates for depression ranged from 0% in Vienna and Zurich to 19% in Bordeaux. Rates were significantly lower in Zurich than in Bordeaux (P=0.004), Paris (P=0.023), Porto (P=0.013) and the UK (P=0.017). Although Vienna had no case of depression at the antenatal interview, statistical comparisons with the other centres were not significant, probably because of the small sample sizes. For major depression, antenatal point prevalence rates ranged from 0% in Vienna, Zurich, Florence and Iowa City to 13.6% in the UK. The difference in rates was significant between only Zurich and the UK (P=0.017). The point prevalence rates of antenatal depression indicated by a score of 13+ on the EPDS ranged from 2.5% in Iowa City to 14.3% in Bordeaux, with no significant difference between centres.
Overall, the broadest diagnostic, caseness, had a higher point prevalence rate than the other two diagnostic categories, depression and major depression, at the assessment during pregnancy. This is not surprising since caseness included not only diagnoses of major and minor depression, but of generalised anxiety disorder as well. Vienna and Zurich had the lowest rates of antenatal depression and anxiety examined in this study, whereas Bordeaux, Porto and Dublin had the highest rates of antenatal depression and anxiety.
Postnatal point prevalence rates
The overall postnatal point prevalence rate for caseness was 10.0%, that
for depression was 8.0%, that for major depression was 4.2%, and that for EPDS
13+ was 6.6%. Rates for individual centres are presented in
Table 2.
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View this table: [in a new window] | Table 2 Postnatal point prevalence rates |
Postnatal point prevalence rates for caseness ranged from 0% in Vienna and the UK to 29.2% in Porto. Rates in Porto were significantly higher than those in five of the eight other centres (Vienna, P=0.007; UK, P=0.014; Zurich, P<0.001; Florence, P=0.027; Iowa City, P=0.003). Postnatal point prevalence rates for depression ranged from 0% in Vienna, Dublin, Florence and the UK to 29.2% in Porto. The rate in Porto was significantly higher than that in all the other centres, except Bordeaux and Paris (P range <0.001-0.014). The rate in Bordeaux was also significantly higher than that in Zurich (P=0.046). Current postnatal major depression rates reached a high of 14.6% in Porto with five of the other eight centres reporting no case of major depression at the time of the postnatal interview. The rate for Porto was significantly higher than rates in other centres only for Zurich and Iowa City (P=0.021 and 0.014, respectively), probably because of small sample sizes in the other centres. Postnatal point prevalence rates as indicated by EPDS 13+ ranged from 0% in Bordeaux and Paris to 14.3% in Dublin.
As with overall rates of caseness, depression and major depression during pregnancy, postnatal point prevalence rates for caseness were higher than the rates for the pure categories of depression and major depression. At the postnatal assessment, it was clear that rates of diagnostic depression and anxiety were highest in Porto and Bordeaux. Ironically, Bordeaux along with Paris had the lowest rates of women scoring 13+ on the EPDS at post-partum assessment, although both centres recorded a significant number of women meeting DSM-IV criteria for major or minor depression at that interview. A possible explanation for this discrepancy is that the French validation study of the EPDS found lower cut-off scores to be appropriate in community postnatal assessments (Guedeney & Fermanian, 1998).
Six-month period prevalence rates
Prevalence rates covering the period between the antenatal and postnatal
interviews were adjusted to 6-month period prevalence rates in order to
control for the variation in interval between interviews among the different
centres. The adjusted 6-month period prevalence rate for each country was
calculated by dividing the actual prevalence rate by the average number of
weeks between the antenatal and postnatal interview and then multiplying by 26
weeks (6 months). The adjusted 6-month prevalence rate was used to calculate
the number of cases expected to occur given the sample size of the individual
centre, which was then used in
2 analyses to compare period
prevalence rates between centres. Tables
3,
4 and
5 show
2 values
for adjusted 6-month period prevalence rates for caseness, depression and
major depression. The adjusted 6-month period rates reflect cases that
occurred during the latter part of pregnancy and the post-partum period, and
assume an even distribution of depressive illness across the 26-week
period.
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View this table: [in a new window] | Table 3 Six-month period prevalence rates for caseness (generalised anxiety disorder, major and minor depression): chi-squared comparisons |
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View this table: [in a new window] | Table 4 Six-month period prevalence rates for depression (major and minor): chi-squared comparisons |
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View this table: [in a new window] | Table 5 Six-month period prevalence rates for major depression: chi-squared comparisons |
The overall 6-month period prevalence rates for caseness, depression and major depression were 21.7%, 18.3% and 12.3%, respectively. These rates are consistent with previously reported rates of depression during pregnancy (Cox et al, 1982; Kumar & Robson, 1984; O'Hara, 1986; Kitamura et al, 1993) and the post-partum period (O'Hara & Zekoski, 1988; O'Hara & Swain, 1996).
Period prevalence rates for caseness ranged from a low in Zurich of 6.2% to a high in Porto of 38.3%. The Zurich sample contained significantly fewer women meeting criteria for generalised anxiety disorder or minor or major depression than did Iowa City, Bordeaux, Paris or Porto. Florence also had significantly fewer women meeting caseness criteria than did Bordeaux and Porto. Depression period prevalence rates ranged from 2.1% in Zurich to 31.6% in Bordeaux. The Zurich rate was significantly lower than that in all other centres except Florence. Florence also had significantly lower rates compared with Bordeaux, Paris and Porto for depression. Period prevalence rates for major depression ranged from 0% in Florence to 19.8% in Bordeaux. Rates in Florence and Zurich were significantly lower than those in the UK, Porto, Paris and Bordeaux. Zurich also had significantly fewer cases of major depression than did Dublin.
Overall, 6-month period prevalence rates revealed lower rates of perinatal depression and anxiety in Florence and Zurich and higher rates in Porto, Bordeaux and Paris. Interestingly, although no woman in the Viennese sample met criteria for current generalised anxiety disorder or depression at the time of the antenatal and postnatal interviews, the period prevalence rate indicates that a high percentage of women (16.8%) experienced generalised anxiety disorder and/or major or minor depression during the last part of pregnancy and the early post-partum period.
Other disorders
Period prevalence rates for other disorders were extremely low, at less
than 1% overall for agoraphobia, anorexia and bulimia nervosa, and 1-2% for
panic disorder and obsessive-compulsive disorder. There was no case of alcohol
or substance misuse.
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Interestingly, the overall estimated 6-month period prevalence rate of major depression obtained from the current study (12.3%) is almost identical to the prevalence rate calculated by O'Hara & Swain (1996) in a meta-analysis of 59 postpartum depression studies conducted in several countries - European, Western and non-Western - during the past 20 years. The average prevalence rate for postnatal depression obtained in the meta-analysis was 12% when depression was assessed using standardised interview-based measures. It should be noted that the 6-month prevalence rate obtained in our study reflects not only cases of major depression during the post-partum period, but also cases occurring during the latter part of pregnancy. However, at least 88% of the women who experienced a major depressive disorder between the antenatal and postnatal interviews reported its onset after delivery.
There were significant differences in prevalence rates of perinatal depression among women participating in the various centres. There may be several explanations for the higher rates of perinatal depression observed in Porto, Paris and Bordeaux and the lower rates found in Zurich and Florence. First, it is possible that these differences occurred by chance, given the relatively small sample sizes in some centres. However, there is evidence that rates of depression and psychiatric illness do vary among countries and cultures. Weissman et al (1996) reported wide variation in lifetime rates of major depression across ten countries participating in a cross-national epidemiological survey (USA, Canada, Puerto Rico, France, West Germany, Italy, Lebanon, Taiwan, Korea and New Zealand). In that study, sample size was not a concern as approximately 38 000 persons participated.
Another possible explanation for the difference in prevalence rates
involves rates of previous episodes of depression among women from the various
centres. Previous history of depression is a powerful predictor of perinatal
depression (O'Hara et al,
1991). There were significant differences between centres in rates
of previous depression, ranging from 10% or less in Vienna and Zurich to 50%
and over in Iowa City, Paris and the UK. Overall, there were strong
associations between previous depression and period prevalence of caseness
(
2=7.72, P=0.005), depression
(
2=9.39, P=0.002) and major depression
(
2=16.58, P<0.001). However, when results for
individual centres were examined, these associations were significant only in
the UK and Vienna, and controlling for past history did not remove the
differences between centres. It did not appear, therefore, that different
rates of previous depression could explain the higher rates of perinatal
depression found in Porto, Paris and Bordeaux, or the lower rates in Zurich
and Florence.
Third, there were differences in the demographic characteristics of the
sample, notably in terms of social class, with Porto having a much lower
proportion of women categorised as non-manual class (43%
compared with 64% or more elsewhere). Manual class women were
more likely to experience perinatal caseness (
2=10.91,
P=0.001), depression (
2=6.84, P=0.009) and
major depression (
2=5.38, P=0.02), but again,
controlling for this variable did not remove the differences between
centres.
A fourth hypothesis is that factors related to psychosocial variables associated with depression might have contributed to the higher rates of perinatal depression in Porto, Bordeaux and Paris (Bernazzani et al, 2004, this supplement). Both stressful life events and low levels of emotional support have been associated with postnatal depression (O'Hara & Swain, 1996). Women in Paris experienced more severe life adversity in the form of acute negative life events and chronic daily stresses during their pregnancy and after delivery compared with women in other centres (Bernazzani et al, 2004, this supplement). Poor emotional support following delivery, another psychosocial variable associated with depression, was reported by a higher percentage of women in Porto than women in other centres (Bernazzani et al, 2004, this supplement).
With regard to the low rates of perinatal depression observed in Florence and Zurich, perhaps psychological factors, such as having a positive attitude towards the pregnancy or having a secure maternal attachment style, buffered women from experiencing depression during this period. Women in both Florence and Zurich reported fewer negative feelings towards the pregnancy than women in other centres (Bernazzani et al, 2004, this supplement). Also, fewer women in Zurich had markedly insecure maternal attachment styles and were perhaps less vulnerable to depression during this transitional period in their life. More insights regarding the validity of these hypotheses can be found in Bernazzani et al (2004, this supplement) and Bifulco et al (2004, this supplement).
Finally, differences in health care systems (see Chisholm et al, 2004, this supplement) may also have contributed to centre differences.
In sum, one of the major aims of the TCS-PND was accomplished in that psychiatric researchers were able to use a standardised, structured diagnostic instrument, the SCID-PND, to assess women from varying cultural backgrounds both during pregnancy and postnatally. Although the overall rate of perinatal depression across centres replicated findings from previous individual studies, cross-cultural comparisons of antenatal and postnatal prevalence rates of depression revealed differences in rates between centres. These findings require verification in larger, multi-centre studies.
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LIMITATIONS
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This article has been cited by other articles:
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P. Asten, M. N. Marks, and M. R. Oates Aims, measures, study sites and participant samples of the Transcultural Study of Postnatal Depression The British Journal of Psychiatry, February 1, 2004; 184 (46): s3 - s9. [Abstract] [Full Text] [PDF] |
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