Postnatal psychiatric morbidity: a validation study of the GHQ-12 and the EPDS as screening tools

General Hospital Psychiatry 29 (2007) 1 – 7

Psychiatry and Primary Care Recent epidemiologic studies have found that most patients with mental illness are seen exclusively in primary care medicine. These patients often present with medically unexplained somatic symptoms and utilize at least twice as many health care visits as controls. There has been an exponential growth in studies in this interface between primary care and psychiatry in the last 10 years. This special section, edited by Ju¨rgen Unutzer, M.D., will publish informative research articles that address primary care-psychiatric issues.

Postnatal psychiatric morbidity: a validation study of the GHQ-12 and the EPDS as screening tools Purificacio´n Navarro, B.S.a,4, Carlos Ascaso, B.S., Ph.D.b,c, LluRsa Garcia-Esteve, M.D., Ph.D.a, Jaume Aguado, B.S.b, Anna Torres, B.S.a, Rocı´o Martı´n-Santos, M.D., Ph.D.d,e a

Unit of Perinatal Psychiatry and Gender Research, Hospital Clı´nic Universitari de Barcelona, 08028 Barcelona, Spain b Department of Public Health of the University of Barcelona, 08036 Barcelona, Spain c Institut d’Investigacions Biome`diques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain d Drug Abuse and Psychiatric Department, Hospital del Mar, 08003 Barcelona, Spain e Pharmacology Research Unit, Institut Municipal d’Investigacio´ Me`dica (IMIM), 08003 Barcelona, Spain Received 9 July 2006; accepted 4 October 2006

Abstract Objective: To assess the validity of the 12-Item General Health Questionnaire (GHQ-12) and the Edinburgh Postnatal Depression Scale (EPDS) in screening for the most common postnatal psychiatric morbidities (mood, anxiety and adjustment disorders). Method: A two-phase cross-sectional study was designed. First, a sample of 1453 women visiting at 6 weeks postpartum completed the GHQ12 and the EPDS questionnaires. Second, based upon EPDS outcomes, participants were stratified and randomly selected within each stratum for clinical evaluation [Structured Clinical Interview for DSM-IV (SCID)]. Receiver operating characteristic (ROC) analysis was used. Results: The concurrent validity was satisfactory (0.80). At optimum cut-off scores, both GHQ-12 and EPDS yielded very good sensitivity (80; 85.5) and specificity (80.4; 85.3), respectively. ROC curves showed that the performance of the EPDS (AUC = 0.933) is slightly superior to that of GHQ-12 (AUC = 0.904). Conclusion: Both GHQ-12 and EPDS are valid instruments to detect postnatal depression as well as postnatal anxiety and adjustment disorders. D 2007 Elsevier Inc. All rights reserved. Keywords: EPDS; GHQ-12; Validation; Postnatal anxiety; Postnatal depression

1. Introduction Postnatal mental disorders are common, disabling and frequently undiagnosed in primary care, with prevalence rates ranging from 8.7% to 18% [1,2]. Most research has been focused on postnatal depression (PND) which affects 10–13% of mothers after delivery [3,4]; although recent evidence suggests that postnatal anxiety disorders may be more common than PND [5].

4 Corresponding author. Purificacio´ n Navarro Garcı´a. Unitat de Psiquiatria Perinatal i de Recerca de Ge`nere (UPPiRG), Hospital Maternitat, 08028 Barcelona, Spain. Tel.: +34 932275600; fax: +34 932275605. E-mail address: [email protected] (P. Navarro). 0163-8343/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.genhosppsych.2006.10.004

Postnatal anxiety has been considered a feature of postpartum depression [6] or a specific anxiety disorder, such as generalized anxiety, panic, obsessive compulsive disorder or posttraumatic stress disorder [5]. In a recent metaanalysis, anxiety during pregnancy was found to be a strong to moderate risk factor for postnatal depression [7]. Growing evidence indicates that maternal anxiety and depression during pregnancy [8,9] and the postpartum period [10,11] can negatively affect infant welfare. As Stewart [12] pointed out, bwhat is special about maternal mood disorders in the perinatal period is the impact they may have on the health and well-being of the woman, foetus and the family.Q In this context, screening patients for early postnatal detection of both anxiety and depression is necessary.

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Although there is an ongoing debate on the usefulness and psychometric properties of screening measures of perinatal psychopathology [13], more research is clearly needed in this field. The General Health Questionnaire (GHQ) [14] and the Edinburgh Postnatal Depression Scale (EPDS) [15] are two well-known rating scales potentially applicable for the detection of postnatal psychiatric morbidity. The GHQ is a self-administered questionnaire originally designed to detect common mental disorders, such as depression and anxiety, among general medical outpatients and in the community. Multiple-item versions have been shown to have good reliability and validity in general populations, including the 12-, 28-, 30- and 60-item versions. However, few studies have carried out a postpartum validation of the GHQ (12-, 28- and 30-item versions) and in these studies only a case criterion for depression was used [2,16,17]. In a recent review of screening instruments for PND, Boyd et al. [18] recommended the 12-item GHQ because this version is the shortest and has a slightly higher sensitivity and positive predictive value. To our knowledge, no version of the GHQ has been validated in postpartum women using a case criterion for anxiety and depression. In contrast to the GHQ, the EPDS is a 10-item selfadministered scale specifically designed for screening PND [15]. Extensive data about the validity and reliability of this instrument have been generated for different languages and cultures [19]. Cox et al. [15] stated that the EPDS is a onedimensional instrument, but confirmatory factor analysis carried out by Pop et al. [20] found two distinct factors called bdepressive feelingsQ and bcognitive anxiety.Q The presence of two factors has been replicated by others using exploratory factor analyses [21,22]. Furthermore, the total score of EPDS rather than its anxiety subscale [23] has shown a higher correlation with other anxiety measures, such as the State-Trait Anxiety Inventory [24]. In another longitudinal study, the anxiety subscale of the EPDS explained 38% of the total EPDS score at 6 weeks postpartum [6]. These findings indicate that EPDS has a strong anxiety component and is not a direct measure of depression. Therefore, it could be used as a measure of dysphoria or distress as hypothesized by Green [21]. A single validation study to identify postpartum women diagnosed with major and minor depression, panic disorder and acute adjustment disorder with anxiety showed good sensitivity and specificity [25]. The authors recommended a lower EPDS cut-off (7/8) than that suggested by most researchers who used the EPDS to screen for major and minor depression. However, this study explored a limited range of anxiety disorders and was carried out in primiparous who were recruited from antenatal parenthood classes, with a subsequent selection bias. Furthermore, concurrent validity of the EPDS was tested among other measures of depression, but a reliable measure of distress such as GHQ was not included. The present study was designed with two objectives: (1) to validate the GHQ-12 and the EPDS questionnaires for the

screening of postnatal psychiatric morbidity in a large sample of childbearing women using the Structured Clinical Interview for DSM-IV (SCID) as the gold standard for diagnosing anxiety, depression and adjustment disorders; and (2) to compare the performance of the GHQ-12 and the EPDS instruments using a case criterion for anxiety and depression. 2. Methods 2.1. Study population A case control, two-phase cross-sectional study was designed to validate the GHQ-12 and the EPDS for detection of postnatal psychiatric morbidity. The study protocol was approved by the institutional review board. All participants gave written informed consent. All Spanish women consecutively visiting for routine postnatal followup at 6 weeks after delivery at the Obstetrics and Gynaecology Unit of an acute-care teaching hospital in Barcelona over a 1-year period were eligible and gave written informed consent. Illiterate women were excluded as were those who had a dead newborn. In Phase 1, all mothers who met the inclusion criteria were approached by a trained research assistant who fully explained the study, obtained the written informed consent and administered a sociodemographic protocol and the screening tools (EPDS and GHQ). Participants were stratified into four levels according to their EPDS score as follows: b 7; = 7 and b 10; = 10 and b 13; and = 13. In Phase 2, approximately 30% of participants in the previous phase were randomly selected using a stratified multi-stage sampling design. In order to ensure adequate rates of anxiety, depression and adjustment disorders, a random sample including 15% of women with EPDS score b 7; 50% with EPDS score =7 and b10; 60% with EPDS score = 10 and b13; and 100% with EPDS score = 13 were selected. All participants in Phase 2 were assessed by two senior clinicians who were blind to the EPDS and GHQ scores. All mothers clinically diagnosed as a bcaseQ were referred for pharmacological/psychological treatment. 2.2. Assessment instruments All participants in Phase 1 completed a sociodemographic form that included age, education level, marital status, number of children and employment status during pregnancy, Table 1 EPDS score distribution in the two-phase sampling EPDS scores

Phase 1

Phase 2

n

n

%

0–6 7–9 10–12 z 13

1031 181 102 139

134 84 58 129

13 46.4 56.9 92.8

Total participants

1453

405

P. Navarro et al. / General Hospital Psychiatry 29 (2007) 1–7

episode (DSM-IV, Appendix B) and disthymia]; (2) anxiety disorders [generalized anxiety disorder (GAD), including the 6-month duration criterion, panic disorder with or without agoraphobia (PD), agoraphobia (AG), social phobia (SOC), obsessive compulsive disorder (OCD), posttraumatic stress disorder (PTSD) and nonspecified anxiety, including all woman who met all the GAD criteria except for the 6-month duration criterion or subthreshold forms of fear about the health or breathing of the newborn or leaving the house without a companion]; (3) adjustment disorders (all cases precipitated by life events apart from delivery, such as illnesses, newborn hospital admission, partner relationship problems, partner violence, and economic or work difficulties); and (4) other diagnosis. Before initiation of the study, 40 postpartum women were assessed by two trained senior clinicians using the SCID-NP version over a 3-day period (interrated reliability study).

Table 2 Sociodemographic characteristics of Phase 1 participants Sociodemographic characteristics

Phase 1 (n = 1453)

Age (years) V 18 19–34 z 35 Level of education None Primary Secondary Superior Marital status Cohabiting or married Single Parity Primiparous Secundiparous Multiparous Pregnancy employment status Employed Unemployed

n

%

18 1044 391

1.2 71.9 26.9

89 412 533 419

6.1 28.4 36.7 28.8

1422 31

97.9 2.1

878 470 105

60.4 32.3 7.2

1126 327

77.5 22.5

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2.3. Statistical analysis

as well as the Spanish versions of the GHQ-12 [26] and the EPDS [27]. The EPDS [15] is a 10-item self-administered scale with four possible responses and a total score from 0 to 30. The Spanish version of the EPDS was translated and validated for postpartum depression in a previous study [27]. The best cut-off was 10/11 for combined major and minor depression, with a 79% sensitivity, 95.5% specificity, 63.2% positive predictive value and 97.7% negative predictive value. Using this 10/11 cut-off score, we detected all cases of major depression [27]. The GHQ-12 contains 12 items of the original 60-item GHQ version that evaluate the psychiatric morbidity using a four-level alternative response scale. In the general population, the Spanish GHQ-12 version has shown 76% sensitivity and 80% specificity at the optimal cut-off score of 2/3 [26]. The total score varies from 0 to 12. In the present study, the GHQ-12 was used and scored in a bimodal fashion (0-0-1-1). On the same day, the SCID nonpatient version (NP) [28] was performed in shift by both a trained senior psychiatrist (LG) and a clinical psychologist (PN) to establish psychiatric diagnoses. DSM-IV diagnostic groups included were as follows: (1) mood disorders [major or minor depression

Sociodemographic characteristics were summarized by descriptive statistics. Frequency and percentages were used for categorical variables, whereas mean and standard deviations were used for quantitative variables. The distribution of the GHQ and EPDS scores by diagnostic groups was described using box-plot diagrams in which the median, interquartile range (25th–75th) and outliers are represented graphically. Respondents and nonrespondents in Phase 2 were compared (sociodemographic and GHQ and EPDS scores) by two-tailed v 2 and Student’s t-tests. Comparisons between mean GHQ and EPDS scores by diagnostic groups were performed by nonparametric analysis of variance models (Kruskal–Wallis test). Post hoc comparisons were performed using the Mann–Whitney U test with the Bonferroni’s correction [29]. To establish concurrent validity, the Spearman correlation coefficient was computed among the EPDS and GHQ scores because the distribution of test scores departed from normality. The agreement between interrater diagnosis was calculated by using the kappa statistics and the 95% confidence interval (CI) [30]. Values range from 100 (perfect agreement) to 1.00 (total disagreement). Kappa values of .75 and higher indicate excellent agreement, values from .65 to .74 indicate good agreement, values from .40 to .64 indicate fair

Table 3 Median, mean and standard deviation of the GHQ-12 and EPDS scores and post hoc comparisons by diagnostic groups Controls (n = 225)

DEP (n = 103)

ANX (n = 23)

ADJ (n = 38)

ANX-DEP (n = 12)

OTH44n = 5)

Median Mean S.D. Median Mean S.D. Median Mean S.D. Median Mean S.D. Median Mean S.D. Median Mean S.D. GHQ-12 1

2.3

2.4

8

8.1

2.8

7

6.3

2.6

6

6.2

3.0

8.5

8

2.9

5

6

4.3

EPDS

5.3

4.1

15

15.6

4.2

11

11.6

4.3

11.5

11.9

3.7

16.5

17.5

5.2

12.5

12.5

6.0

5

Post hoc comparisons4 DEP, ANX–DEP, ANX, ADJ N controls DEP, ANX–DEP NANX, ADJ N controls

DEP, Depression; ANX, anxiety; ADJ, adjustment; ANX–DEP, comorbid anxiety and depression; OTH, others. 4 All post hoc comparisons are significant at P b.0001. 44 The OTH group showed no statistically significant differences with the remaining groups because the power of the test was limited due to the small sample size.

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3. Results 3.1. Characteristics of participants 3.1.1. Phase 1 A total of 1591 women were approached but 84 did not meet the inclusion criteria. Of the remaining 1507 eligible women, 54 refused to participate in the study. Therefore, 1453 (96.4%) women completed the screening phase (Table 1). The mean age of the participants was 31.7 years (range, 18–46 years). Only 6% had no primary education and 65% completed high school or held a university degree. Ninety-eight percent of the women were living with a partner, 60% were first-time mothers and 77.5% had been employed during pregnancy (see Table 2).

Fig. 1. Box diagram and distribution of the GHQ-12 and the EPDS scores (median, quartiles and outliers) by diagnostic groups.

agreement, and values of .39 or lower indicate poor agreement [30]. Sensitivity, specificity and the number needed to diagnose (NND) were calculated for a range of cut-off scores against SCID diagnosis. The formula NND = 1/ [sensitivity (1 specificity)] indicates the number of tests that need to be undertaken in order to gain a positive response for the presence of the disease [31]. The NND was chosen instead of the positive predictive value (PPV), because PPV provides test performance characteristics that fluctuate markedly as a function of the prevalence of the target disorder (in the present study, due to our sampling design, the ratio case/no case is not the prevalence). In contrast, NND is a function of sensitivity and specificity, which are reproducible test performance characteristics that tend to remain highly stable across populations [31]. Receiver operating characteristic (ROC) curves were also constructed, and the area under the curve (AUC) was calculated by means of trapezoidal rule [32] with 95% CI. Receiver operating characteristic curves allow the exploration of the entire range of sensitivities and specificities at each possible cut-off score. One major advantage is that ROC curves and AUC values are independent of an arbitrary choice of a discriminant threshold [32]. Analyses were performed with SPSS (version 11.5.1) and STATA (version 7.0) computer programs. Statistical significance was set at P b.05.

3.1.2. Phase 2 A total of 428 women were eligible for Phase 2 of the study; 23 of whom withdrew their informed consent. Thus, 405 (94.6%) women completed the interview phase. Table 1 shows the number and percentage of mothers selected for interview with the SCID by each level of EPDS. Nonrespondents were not significantly different than responders with regard to age, education level and either EPDS or GHQ12 scores. The nonrespondents compared with respondents were more likely to be multiparous (65.2% vs. 35.9%; v 2 =8.04; df = 1; P b.005) and unemployed during pregnancy (39.1% vs. 18.3%; v 2 =6.1; df =1; P =.014). Among the 405 women who were interviewed with the SCID, 180 participants met the DSM-IV criteria for at least one Axis I disorder at 6 weeks postpartum, while the remaining 225 did not (Table 3). The results of the interrater reliability with the SCID were excellent for mood disorders (kappa = .80) and anxiety disorders (kappa =.77), and good for adjustment disorders (kappa =.70). 3.2. Mean GHQ-12 and EPDS scores by diagnostic groups Fig. 1 shows the box diagram and distribution of GHQ12 and EPDS scores for cases and controls. Table 3 shows the median, mean and S.D., and post hoc comparisons for

Fig. 2. Receiver operating characteristic curve of the GHQ-12 and the EPDS.

P. Navarro et al. / General Hospital Psychiatry 29 (2007) 1–7 Table 4 Sensitivity, specificity and NND of the GHQ-12 and the EPDS Sensitivity (95%CI)

Specificity (95%CI)

NND

(96.9–99.9) (96.9–99.9) (89.3–96.6) (81.4–91.7) (74.0–86.1) (66.8–80.1) (56.4–70.9)

30.2 50.2 63.6 72.2 80.4 89.3 94.2

(24.3–36.7) (43.5–56.9) (56.9–69.8) (66.6–77.9) (74.6–85.4) (84.5–93.0) (90.3–96.9)

3.4 2.0 1.7 1.7 1.6 1.6 1.7

EPDS cut-off 6/7 98.3 (95.2–99.6) 7/8 95.0 (90.7–97.7) 8/9 90.0 (84.6–93.9) 9/10 85.5 (79.5–90.3) 10/11 81.1 (74.6–86.6) 11/12 74.4 (76.4–80.6) 12/13 66.6 (59.2–73.5) 13/14 56.7 (49.1–64.1)

57.8 66.7 77.8 85.3 88.9 93.8 96.0 97.3

(51.3–46.3) (60.1–72.8) (71.8–83.1) (80.1–89.7) (84.1–92.7) (89.8–96.6) (92.6–98.2) (94.3–99.1)

1.8 1.6 1.5 1.4 1.4 1.5 1.6 1.9

GH-12 cut-off 0/1 99.4 1/2 99.4 2/3 93.8 3/4 87.2 4/5 80.6 5/6 73.9 6/7 63.9

GHQ-12 and EPDS by diagnostic groups. Post hoc analyses for the GHQ-12 only showed statistical significant differences between the no-diagnosis group and the remaining groups ( P b.003). Post hoc analyses revealed that the mean EPDS scores of the groups with pure depression and comorbid anxiety–depression were higher than those of the groups with pure anxiety and adjustment disorders ( P b.003), which were in turn higher than the mean score of the no-diagnosis group ( P b.003). The bother diagnosisQ group showed no significant differences with any of the other groups, even though the power of the test was limited because of the small sample size (n =5). 3.3. Validation of the GHQ-12 and the EPDS for detection of postnatal psychiatric morbidity The psychometric performance of the GHQ-12 and the EPDS in screening common postnatal psychiatric morbidity is summarized in a ROC curve (Fig. 2). The AUC values for both screening tools are above 0.9, indicating an excellent validity for both measures with better results for EPDS (AUC = 0.933; 95% CI =0.910–0.956) than for GHQ-12 (AUC = 0.904; 95% CI= 0.876–0.932). The statistical comparison of the AUC values revealed a significant difference between both measures (v 2 = 4.5; P = .0338), favouring EPDS as a slightly more powerful screening tool. According to the ROC curve, 4/5 was the optimal cut-off score for the GHQ-12, with 80.6% sensitivity (95% CI = 74.0–86.1), 80.4% specificity (95% CI = 74.6–85.4) and 1.6 NND (95% CI =1.4–2.1). For the EPDS, the optimal cut-off score was 9/10, with 85.5% sensitivity (95% CI= 79.5–90.3), 85.3% specificity (95% CI =80.1–89.7) and 1.4 NND (95% CI = 1.3–1.7). The cut-off scores of the GHQ-12 and the EPDS for postnatal psychiatric morbidity are summarized in Table 4. Assuming these optimal cut-off scores, the EPDS identified a higher number of cases with depression

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diagnosis (with or without comorbid anxiety) than GHQ (110 vs. 100); although both screening tests identified almost the same number of cases with pure anxiety (15 vs. 16) and with adjustment disorders (27 vs. 27). In agreement with these findings, the EPDS showed a superior sensitivity, especially for mood disorder group. The EPDS showed a high correlation with the GHQ-12 (r 2 =.80; P b.0001).

4. Discussion Our results indicate that both GHQ-12 and EPDS are useful short screening tools for the assessment of the more frequent postnatal psychiatric morbidity. Both scales had good sensitivity and specificity when diagnosis of caseness is broadened to include anxiety, depression and adjustment disorders. The good concurrent validity of the EPDS against the GHQ scores, with a value of 0.80, also supports the similarity between both instruments. At optimal cut-off scores, the GHQ and the EPDS are able to detect 80.6% and 85.5% of postnatal cases, with a NND of 1.6 and 1.4, respectively. The comparison of the AUC of both instruments showed a slightly better performance for the EPDS. To our knowledge, this is the first study in which the GHQ has been validated for screening anxiety and depression in postpartum women. The AUC value of 0.91 in this study has fallen in the superior limit of AUC values, which ranged from 0.78 to 0.95, as reported for the GHQ-12 in studies carried out in general health care and community settings [33,34]. An optimal cut-off score of 4/5 is able to detect 80.6% of psychiatric caseness and reaches a specificity of 80.4%, supporting its excellent performance as a screening instrument. This optimum cut-off score was also chosen in postpartum Chinese women to identify only DSM-IV major and minor depression [17]. Despite differences in severity of case criterion, this coincidence may be a reflection of genuine cultural or ethnic characteristics. Women from non-Western countries refer somatic rather than psychiatric symptoms when suffering from anxiety or depression states [35], and the GHQ-12 does not contain items about somatic symptoms. For our study population, we found that using the 1/2 and 2/3 cut-off scores as normally recommended for psychiatric cases in a nonpostpartum context, including Spanish community setting [26], would yield an unsatisfactory specificity and sensitivity. It suggests that postpartum women scored higher on the GHQ than the general population and might reflect the usual high levels of stress and disorganization associated with the transition to parenthood [36]. Tarnopolsky et al. [37] also found that people with heavy domestic charges showed more false-positive results in the GHQ than the general population. Thus, self-rating measures designed for nonpostpartum context need to be modified [17]. We have validated for the first time the EPDS against a full range of DSM-IV diagnosis, and the results obtained are encouraging. Descriptive data showed that all diagnostic

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groups had mean EPDS scores higher than threshold (10/11) validated for postpartum depression in Spanish women [27]. Comparison by diagnostic groups showed that the EPDS scores were sensitive to the type of disorders and gradually increased in accordance with diagnostic groups. It should be noted that women with comorbid anxiety–depression had the highest scores, even though there were no significant differences given the relatively small group size (n = 12), suggesting a possible gradient of severity. These findings are not in agreement with data reported by Muzik et al. [38], who found that the EPDS was not suitable to distinguish between anxiety cases and controls. A limitation of this study, however, was the small sample size of all comparison groups. We found an optimum EPDS cut-off of 9/10 for screening postnatal psychiatric morbidity which is higher than the 7/8 reported by Matthey et al. [25]. This difference may be explained by the different coverage of DSM-IV disorders, as well as the lower rate of major depression found in this study. Our results suggest that postpartum women who scored above the threshold on screening depression questionnaires have a broad range of psychiatric illness [39]. Hence, this supports that maladjustment in the postpartum period may not necessarily be confined to depression. Besides depression, a group of conditions that are clinically relevant because they are associated with substantial life interference and distress, according to DSMIV criteria, were detected. These included a wide range of disorders (agoraphobia, panic, GAD, OCD and PTSD), as well as some minor disorders generally, namely, postnatal distress [40], such as nonspecific anxiety disorders and adjustment disorders, which need to be correctly identified and addressed with specific treatment approach. Moreover, it has been reported that these disorders may also have a negative impact on the infant’s well-being [10]. Comparing the use of the EPDS and GHQ-12, we found that both EPDS and GHQ-12 have good sensitivities and specificities in detecting the more common psychiatric morbidity when the optimal cut-off scores were used. Although EPDS seems to be a slightly more powerful screening tool. The higher correspondence between both screening tools concerning concurrent validity and psychometric parameters (sensitivity, specificity and NND values) supports and adds evidence to the hypothesis of Green [21], suggesting that the EPDS may be a good measure of dysphoria or distress, such as the GHQ. The study has some limitations. The sample was only stratified by EPDS scores. However, representativeness of the EPDS stratum is broader and percentages are higher than those typically used in case-control studies. Because subjects were recruited from community settings, our results cannot be generalized to other postpartum population. It will be necessary to explore their utility in different settings (clinical vs. research samples) and countries [41]. This study has a number of strengths. The administration of both screening scales and SCID interview was performed on the same day. Studies with a different time gap obtained a lower

cut-off score in the EPDS [25]. The higher response rate obtained in Phases 1 and 2 ensures the sample representativeness and data interpretation. Finally, we decided to use the NND, instead of the PPV, because it is not affected by the prevalence of the condition of interest [31]. In conclusion, the present results indicate that both EPDS and GHQ are useful instruments for detecting postnatal psychiatric morbidity. We recommend a higher cut-off score when the GHQ-12 is applied in the postpartum period. The EPDS can be used to detect both depression and anxiety, or depression only, depending on the EPDS cut-off used. We propose a lower EPDS cut-off to detect both depression and anxiety than the commonly accepted for postpartum major depression.

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