- Email: [email protected]
Comparison of scoring methods and thresholds of the General Health Questionnaire-12 with the Edinburgh Postnatal Depression Scale in English women
Public Health 123 (2009) 789–793
Contents lists available at ScienceDirect
Public Health journal homepage: www.elsevierhealth.com/journals/pubh
Original Research
Comparison of scoring methods and thresholds of the General Health Questionnaire-12 with the Edinburgh Postnatal Depression Scale in English women N.J. Shelton a, *, K.G. Herrick b a b
Department of Epidemiology and Public Health, University College London (UCL), 1–19 Torrington Place, London WC1E 6BT, UK Nutrition and Health Sciences, Emory University, Atlanta, GA 30322, USA
a r t i c l e i n f o
s u m m a r y
Article history: Received 15 May 2009 Received in revised form 8 September 2009 Accepted 22 September 2009 Available online 17 November 2009
Objectives: To compare the scoring methods and thresholds of the 12-item General Health Questionnaire (GHQ-12) and the Edinburgh Postnatal Depression Scale (EPDS) in English women, and to determine which threshold and scoring method provides the closest correlation of caseness of postnatal depression in a nationally representative sample of English women. Study design: Health Survey for England 2002 health examination survey. Methods: Self-completion booklet containing the EPDS and the GHQ-12. Participants were mothers with at least one child under 1 year of age at the time of interview. Results: Both the scoring method and cut-off affected the estimates of prevalence of postnatal depression in English women. The best threshold and scoring method for the GHQ-12 using sensitivity/specificity analysis against the EPDS was a standard scale with a cut-off of 3þ. This matched the cut-off using the GHQ-12 mean scores. The cut-off using comparative prevalence of the GHQ-12 with the EPDS was higher at 4þ. There was a significantly lower estimate of prevalence of postnatal depression at 4 months using the GHQ-12. Conclusions: Care needs to be taken measuring postnatal depression. The GHQ-12 mean score cut-off matched the cut-off using sensitivity and specificity; this supports using the GHQ-12 mean scores as cutoffs. The standard scale was most closely correlated with the EPDS. Although there was strong correlation between the GHQ-12 and the EPDS, a significantly lower proportion of women were measured as having possible postnatal depression at 4 months using the GHQ-12. This may be due to the lack of a question on blame in the GHQ-12. Four months coincided with the duration of maternity leave entitlement and recommended age for weaning in 2002. These events may be particularly stressful for mothers, and practitioners need to be mindful of similar milestones for diagnosis if using the GHQ-12. Ó 2009 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
Keywords: Postpartum depression Postnatal depression GHQ-12 Health Survey for England EPDS
Introduction Postnatal depression can have profound effects on mothers, infants and the wider family. The prevalence of postnatal depression has been estimated at approximately 10% in recently delivered women in the UK,1 and between 10% and 15% internationally.2,3 Correctly identifying postnatal depression is a key concern for healthcare professionals. In the UK, this is usually done by general practitioners or midwives via short questionnaires completed after childbirth. Two commonly used screening instruments in clinical and epidemiological settings are the Edinburgh Postnatal
* Corresponding author. Tel.: þ44 (0)20 7679 5648; fax: þ44 (0)20 7813 0242. E-mail address: [email protected] (N.J. Shelton).
Depression Scale (EPDS) and the General Health Questionnaire (GHQ). The EPDS is a dedicated 10-item postnatal depression screening tool, whilst the GHQ is a 60-item screening tool for nonpsychiatric morbidity, commonly found in shortened versions of 30 (GHQ-30) and 12 (GHQ-12) items. Both the EPDS and the GHQ are currently used to screen for depression. The EPDS, introduced in 1987, was developed as a self-administered tool for use in clinical and research settings to identify mothers at risk of postnatal depression.4,5 The scale is composed of 10 questions that a mother completes by selecting the answer that best describes her feelings over the past 7 days. Each question is given a score; summed, these questions provide an overall score on the instrument. A bimodal threshold exists for the instrument.6 When identifying ‘definite major depression’, the threshold of 12/ 13 is recommended, whereas the threshold of 9/10 is
0033-3506/$ – see front matter Ó 2009 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.puhe.2009.09.012
790
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793
recommended for screening in the community. Timing is also important in the use of the EPDS. Studies have shown that half of all cases of postnatal depression start within the first 3 months and three-quarters within the first 6 months after childbirth 7; therefore, three contact points during which the scale could be administered are recommended. The current suggested times for use are 5–8, 10–14 and 20–26 weeks postnatally. Since its introduction, there have been validation studies in many languages and in populations with varied socio-economic backgrounds.4 It is considered the ‘gold standard’ of self-administered questionnaires and the instrument of choice when the outcome of interest is postnatal depression. The GHQ-12, a shortened version of a 60-item screening tool developed by Goldberg in 1970, is a screening instrument for depression/general non-psychiatric morbidities.8 It comprises 12 questions, six of which are positively phrased and six negatively phrased, with a five-option ‘more/less than usual’ response. Three scoring methods are commonly used. These are the original scale (for absence or presence of condition), and two other less frequently used scales: the Likert and the chronic scales.9 With the Likert scale, each component is scored on a five-point scale relating to severity. On the chronic scale, the response ‘no more than usual’ is considered to be indicative of ill health for the six negatively worded questions and scored. In general clinical settings, higher thresholds may be required to identify cases, as higher GHQ scores are expected as a consequence of symptoms of physical illness.10 The GHQ has been used in many populations and translated into several languages.10–12 It has been claimed that ‘the GHQ-12 can be used and should be preferred in all clinical settings for screening and case detection’ of psychological disorders.13 Its use in postnatal settings has been well documented 14,15; however, this same literature disagrees on the most appropriate threshold and even scoring method. Generally, higher cut-offs are often used in postnatal settings, e.g. 4/513 compared with 1/2 or 2/3 in general populations.10 All of the aforementioned thresholds apply to the most commonly used scoring method, not the Likert or chronic scales. It has also been argued that the GHQ-12 had a broader coverage of neurotic conditions, and so was ‘potentially superior’ to the EPDS and could identify somatic illness.15 Contradictory to these studies, a study examining the case identification properties of the GHQ-12 using three different scoring methods concluded that the GHQ-12 was not recommended to identify psychological distress in postnatal samples.16 The disagreement between these studies highlights a debate that has followed the GHQ since its invention: how does one select the appropriate threshold for the sample of interest? The recommendation from the scale’s author is to carry out a validation study in the population of interest,8 but the associated expense and impracticality is often a deterrent. Thus, in 1998, the GHQ’s author and others recommended an alternative to a validation study; the mean score method to set a crude threshold.17 Martin and Jomeen used this approach in their study of 58 pregnant women and still felt it was inadequate. As the three GHQ-12 scales gave conflicting levels of possible depression, they asserted the notion that the scale should be validated in every setting prior to use; this is not feasible.16 As their study did not use a clinical screening instrument or screening questionnaire for comparison, it is impossible to tell which, if any, of the scales would have been appropriate, or if they should have chosen different cut-offs for each scale. Retrospective significance tests and power calculations based on the small sample size of the Martin and Jomeen paper carried out for this research (results not shown) showed that, despite the differences in prevalence being large (approximately 20%), they were not statistically significant and the power of the study was low. More recently, Navarro et al. argued that both the
EPDS and the GHQ are useful instruments for detecting postnatal psychiatric morbidity.18 To compare postnatal women with the wider population, a more comprehensive scale such as the GHQ-12 in a survey setting may be useful. However, when using the GHQ-12, which threshold and scoring method provides closest correlation of caseness of postnatal depression between the GHQ-12 and the EPDS, and to what extent does the choice of measurement tool, scoring method and cut-off affect the estimates of prevalence of postnatal depression? The EPDS has the advantage that it is shorter (10 questions compared with 12) and therefore cheaper and quicker to deliver, so if postnatal depression is the outcome of interest, it may be the preferred instrument. However, the EPDS is limited to postnatal depression and was not designed to pick up somatic illness.4 Several studies have argued that the EPDS is not only applicable postnatally, but can be suitable for other groups of women19 including pregnant women20 and even new fathers.21,22 There is also debate in the literature regarding the latest point at which postnatal depression can be diagnosed; i.e. when is a diagnosis of depression for women with children no longer a diagnosis of postnatal depression?13 The EPDS authors recommend 6 months. Methods The Health Survey for England (HSE) is an annual survey designed to monitor the health of people living in England, and seeks to inform policy aimed at improving their health. Core statistics are collected each year, and additional modules focus on specific demographic groups or disease conditions in different years. The first survey was conducted in 1991, and the twelfth in the series, the 2002 report (used here), comprised the standard random cluster, cross-section sample designed to be representative of the English population, as well as the inclusion of a new module (Maternal and Infant Health). Further details of the full survey can be found in the HSE 2002 report.23 Ethical approval was obtained from the London Multi-centre Research Ethics Committee. During the interview stage of the survey, mothers were approached at home and asked to fill out a self-completion booklet which contained both the EPDS and the GHQ-12. The inclusion criterion used for the Maternal and infant Health Module was mothers with an infant aged under 1 year at the time of interview (n ¼ 399). Of these, 394 mothers (98.7%) had both valid GHQ-12 scores and EPDS scores. Their demographics were not found to differ significantly from non-responders with regards to age, parity, time since childbirth, social support, occupation of the household reference person, index of multiple deprivation, or lone- or twoparent household (data not shown). Mothers were interviewed at a random time point within the infant’s first year of life; both the GHQ-12 and the EPDS were administered in the same interview. Three scoring methods were used here for responses to the GHQ-12. These were the standard GHQ-12 method (0011 – zeros for positive or neutral response), the Likert type method (0123 – scoring increases with increased negativity of responses) and the chronic method (scores negative questions 0111: zeroes for positive responses only; positive questions 0011: zeroes for positive and neutral responses). Cut-offs were calculated for caseness using two methods: correlation of the GHQ-12 with the EPDS, and the GHQ12 mean score (the mean score in the study population was calculated and this was used as the threshold). Results Table 1 shows the percentage of possible postnatal depression in women using several different scales. The prevalence was 24.4% using the EPDS with community (10þ) threshold. The general,
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793 Table 1 Prevalence of postnatal depression for the Edinburgh Postnatal Depression Scale (EPDS) and different General Health Questionnaire-12 (GHQ-12) cut-offs and scoring methods. GHQ-12 3þ
GHQ-12 4þ
GHQ-12C 6þ
GHQ-12C 7þ
GHQ-12L 14þ
GHQ12L 15þ
24.4
27.9
21.1
34.5
22.3
24.6
20.6
GHQ-12, standard scoring method; GHQ-12C, chronic scoring method; GHQ-12L, Likert-type scoring method.
14 12 10 Mean score
EPDS 10þ
791
EPDS GHQ12-L GHQ12-C GHQ-12
8 6 4 2
Likert and chronic scoring methods were then used with the GHQ12 to estimate the level of possible postnatal depression in the sample. The thresholds for the GHQ-12 were chosen to maximize similarity in the proportion of cases between the GHQ-12 and the EPDS. This identified a threshold of 4/5 for GHQ-12, 7/8 for the chronic scale (GHQ-12C) and 14/15 for the Likert scale (GHQ12-L). In contrast, using the mean scores method led to lower cut-offs: 2/3 for GHQ-12, 4/5 for GHQ-12C and 11/12 for GHQ12-L, and a higher prevalence of caseness than the EPDS. Table 2 shows the sensitivity and specificity of the GHQ-12 compared with the EPDS. Using an average of sensitivity (the proportion of cases correctly identified by test) and specificity (the proportion of non-cases correctly identified by test) for identifying postnatal depression, this test identified 2/3 as the best cut-off for GHQ-12, 3/4 for GHQ-12C and 7/8 for GHQ-12L. Fig. 1 presents mothers’ mean scores for the EPDS and the GHQ-12 scored three different ways by age of infant in months. Looking at the variation in depression by infant age between the different scales in more detail, there was reasonable correlation between the scoring methods over time, except at 4 months when the EPDS showed an upward spike and the GHQ-12 showed a plateau (Fig. 1). This difference was statistically significant (P < 0.000, confidence interval 3.330–0.550, n ¼ 27) and would result in mothers being identified using the EPDS but not the GHQ-12. This difference was not identifiable from the prevalence of postnatal depression at 3–5 months, nor when the prevalences at 4 months were compared, although the sample size was small (data not shown).
Table 2 Performance of General Health Questionnaire-12 (GHQ-12) scales against the Edinburgh Postnatal Depression Scale (EPDS). Cut-off
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
2/3 3/4 4/5
65 59 50
85 92 96
61 74 81
87 86 84
3/4 4/5 5/6
93 88 78
51 64 80
41 48 59
95 93 91
GHQ-12 HSE 2002 Romito et al.13 GHQ-12C HSE 2002 GHQ-12L HSE 2002 Politi et al.25
Piccinelli et al.24
7/8 8/9 9/10 10/11 11/12 12/13 13/14 14/15
98 96 95 90 83 76 67 61
24 40 52 66 76 84 90 93
32 37 43 49 56 63 71 77
97 97 97 94 92 90 88 87
Sensitivity, proportion of cases correctly identified by test; specificity, proportion of non-cases correctly identified by test; positive predictive value, probability of disease when the test is positive; negative predictive value, probability of disease when the test is negative; GHQ-12, standard scoring method; GHQ-12C, chronic scoring method; GHQ-12L, Likert-type scoring method; HSE, Health Survey for England.
0 0
1
2
3
4
5
6
7
8
9
10 11
Age of infant (months) Figure 1. Mothers’ mean scores for the Edinburgh Postnatal Depression Scale (EPDS) and the 12-item General Health Questionnaire (GHQ-12) scored three different ways, by age of infant in months.
These results raised the question of why the two tools might diverge at 4 months. The GHQ-12 is a measure of general psychological morbidity and the EPDS is a specific measure of depression. Table 3 shows a summary of the topics in the two questionnaires. A correlation matrix was calculated comparing negative/positive responses to the GHQ-12 and the EPDS (data not shown). Responses to two questions from the EPDS showed no significant correlation with any items in the GHQ-12. These were self-harm and blame. Given that the EPDS does not include screening questions for somatic illness, it was thought that this might account for the difference in levels of possible depression found. All items in the GHQ-12 were correlated with one or more responses in the EPDS, despite the lack of screening questions for somatic illness in the EPDS. Although there was a fall in the prevalence of feeling blame at 2 months and a rise at 3 and 4 months, the sample sizes were small and the difference was not significant. Discussion Care needs to be taken when choosing a tool (and cut-off and scoring method) for measuring postnatal depression. The three methods of identifying caseness in GHQ-12 used here – comparison of proportion of cases in the sample between the GHQ-12 and the EPDS, average of sensitivity and specificity compared with the EPDS, and using the GHQ-12 mean score as the cut-off – produced different cut-offs for caseness. The standard scale was most closely associated with the EPDS for each method. The GHQ-12 mean score
Table 3 Topics of questions in the General Health Questionnaire-12 (GHQ-12) and the Edinburgh Postnatal Depression Scale (EPDS). Topic
In both questionnaires
Sleep Strain Overcome Enjoy Unhappy Happy Worth Confidence Concentration Face up Useful Blame Scared/panic Fear Self-harm
X Aspects of X X X X
In GHQ-12 only
In EPDS only
X X X X X X X X X
792
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793
produced the same cut-off (3þ) as the sensitivity/specificity analysis, supporting the use of the mean score method for determining cut-offs. The choice of scale and cut-off for the GHQ-12 altered the estimation of possible postnatal depression among women in this study considerably. A priori, it was thought that the most appropriate scoring method and cut-off point for the GHQ-12 to maximize correlation with the EPDS for women who had recently given birth would be one that took chronic pain into account. However, the standard scale corresponded better with the EPDS than the chronic scale in this study for all cut-offs. Prevalence of the EPDS was used as a method of choosing appropriate cut-off points. For the standard GHQ-12 scale, this identified a cut-off of 4þ (which is the same as that recommended by Romito et al. and Navarro et al.)13,18 for postnatal settings, a cut-off of 7þ for the chronic scale (which is 2 more than that recommended in chronic patients) and a cut-off of 14þ for the Likert scale (which corresponds with Piccinelli et al.24 but not Politi et al.25 who recommended 9þ). According to the receiver operating characteristic curve, 4/5 was the optimal cut-off score for the GHQ-12. For the EPDS, the optimal cut-off score was 9/10. Sensitivity and specificity comparisons with the EPDS identified lower cut-offs (3þ for standard scale) and greater prevalence of caseness with the GHQ-12 than the EPDS, as did the GHQ-12 mean scores. The divergence of caseness between the GHQ-12 and the EPDS at 4 months may require understanding of what was happening in the mothers’ lives at the point when the survey was carried out. Those diagnosing depression may need to review mothers’ postnatal mental health in line with major milestones in the mothers’ and infants’ lives. In 2002, statutory maternity leave was 18 weeks in England.26 Four months may have corresponded with mothers returning to work. Also, the recommended age for weaning an infant was 4 months in 2002,27 which may correspond with a particularly stressful time for the mother. The significantly lower proportion of women measured as having postnatal depression at 4 months using the GHQ-12 compared with the EPDS may be due to inclusion of questions on blame in the EPDS. Milestones in the mother’s life or the infant’s first year may have been the trigger for the higher level of postnatal depression seen in women with infants of this age. Clinicians need to consider that postnatal depression is not necessarily something that starts almost immediately after birth. Screening around these major milestones may be required, and these may vary from woman to woman and change over time with changes in postnatal policies such as maternity leave allowances etc. The EPDS and the GHQ-12 shared many common factors; despite the absence of somatic screening questions in the EPDS, there was significant correlation between all of the GHQ-12 questions and the EPDS questions. The two factors in the EPDS which were not correlated with any questions in the GHQ-12 were blame and self-harm. Lee et al.28 has argued that the best method of identifying postnatal depression using short screening tools is the ‘Double test strategy’, where components of the GHQ-12 are appended to the EPDS. The GHQ-12 offers the opportunity to compare levels of depression in postnatal women with that in other groups. In a clinical setting, false negatives must be reduced at the expense of false positives. The level of false positives compared with false negatives is not as important in survey data, but the magnitude of the error should be small in a survey setting. Some studies argue that the GHQ-12 is a suitable tool for screening and measuring the prevalence of postnatal depression, while others do not. In a review of postpartum depression screening instruments, Boyd et al.29 argued that given the lack of consensus about the utility and psychometric properties of screening measures in both clinical and research settings,
additional research is needed to determine the best measure for large-scale screening efforts for postpartum depression. In addition, this study shows that choice of cut-offs significantly affects estimates of the prevalence of depression, as does the scale type (standard, Likert, chronic). These must also be considered when choosing a method. Using the GHQ-12 mean score method produced a higher estimation of prevalence of postnatal depression than the EPDS, but the closest relationship with sensitivity and specificity supporting its use for determining cut-offs. The limitations of this study were that it had no clinical comparison. A larger sample size would be required to test the relationship between increased EPDS scores at 4 months but not GHQ-12 scores, and questions on blame in the EPDS and not the GHQ-12. Acknowledgements The authors wish to thank Paola Zaninotto, University College London, for advice with statistical analyses, and the anonymous referees for their comments. The authors are grateful to the participants in the Health Survey for England, the field staff and colleagues at the National Centre for Social Research. Ethical approval London Multi-centre Research Ethics Committee. Funding Kirsten Herrick was funded by the Department of Health as part of the team to carry out the Health Surveys for England, but these analyses have been conducted independently of the funders. The views expressed in this paper are those of the authors, not the funding bodies. References 1. MacArthur C, Lewis M, Knox E. Health after childbirth. London: HMSO; 1991. 2. O’Hara MW, Swain AM. Rates and risk of postpartum depression – a metaanalysis. Int Rev Psychiatry 1996;8:37–54. 3. Lee DTS, Yip SK, Chiu HFK, Leung TYS, Chan KPM, Chau IOL, et al. Detecting postnatal depression in Chinese women. Validation of the Chinese version of the Edinburgh Postnatal Depression Scale. Br J Psychiatry 1998;172:433–7. 4. Cox JL, Holden JM, editors. Perinatal psychiatry: use and misuse of the Edinburgh Postnatal Depression Scale. London: Gaskell; 1994. 5. Cox JL, Holden JM, Sagovsky R. Detection of postnatal depression development of the 10-item Edinburgh postnatal depression scale. BMJ 1987;150:782–6. 6. Goodman JH. Paternal postpartum depression, its relationship to maternal postpartum depression, and implications for family health. J Adv Nurs 2004;45:26–35. 7. Cooper PJ, Campbell EA, Day A, Kennerly H, Bond A. Non-psychotic psychiatric disorder after childbirth: a prospective study of prevalence, incidence, course and nature. Br J Psychiatry 1988;152:799–806. 8. Goldberg D. Manual of the General Health Questionnaire. Windsor: NFER-Nelson; 1978. 9. Goodchild ME, Duncan-Jones P. Chronicity and the General Health Questionnaire. Br J Psychiatry 1985;46:55–61. 10. Goldberg DP, Williams P. The user’s guide to the General Health Questionnaire. Windsor: NFER-Nelson; 1988. 11. Nott PN, Cutts A. Validation of the 30-item General Health Questionnaire in postpartum women. Psychol Med 1982;12:409–13. 12. Jacob S, Bhurgra D, Mann AH. The validation of the 12-item General Health Questionnaire among ethnic Indian women living in the United Kingdom. Psychol Med 1997;27:1215–7. 13. Romito P, Saurel-Cubizolles MJ, Lelong N. What makes new mothers unhappy: psychological distress one year after birth in Italy and France. Soc Sci Med 1999;49:1651–61. 14. Werneke U, Goldberg DP, Yalcin I, Ustu¨n BT. The stability of the factor structure of the General Health Questionnaire. Psychol Med 2000;30:823–9. 15. Lee DTS, Yip ASK, Chiu HFK, Leung TYS, Chung TKH. Screening for postnatal depression: are specific instruments mandatory? J Affect Disord 2001;63:233–8. 16. Martin CR, Jomeen J. Is the 12-item General Health Questionnaire (GHQ-12) confounded by scoring methods during pregnancy and following birth? J Reprod Infant Psychol 2003;21:267–78.
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793 17. Goldberg DP, Oldehinkel T, Ormel J. Why GHQ threshold varies from one place to another. Psychol Med 1998;28:915–21. 18. Navarro P, Ascaso C, Garcia-Esteve L, Aguado J, Torres A, Martı´n-Santos R. Postnatal psychiatric morbidity: a validation study of the GHQ-12 and the EPDS as screening tools. Gen Hosp Psychiatry 2007;29:1–7. 19. Cox JL, Chapman G, Murray D, Jones P. Validation of the Edinburgh Postnatal Depression scale (EPDS) in non-postnatal women. J Affect Disord 1996;39:185–9. 20. Murray D, Cox JL. Screening for depression during pregnancy with the Edinburgh Depression Scale (EPDS). J Reprod Infant Psychol 1990;8:99–107. 21. Matthey S, Barnett B, Kavanagh DJ, Howie P. Validation of the Edinburgh Postnatal Depression Scale for men, and comparison of item endorsement with their partners. J Affect Disord 2001;64:175–84. 22. Madsen SA, Juhl T. Paternal depression in the postnatal period assessed with traditional and male depression scales. J Mens Health Gend 2007;4:26–31. 23. Sproston K, Primatesta P. Health Survey for England 2002. Summary of key findings. Volume 1: The health of children and young people; Volume 2: Maternal
24. 25.
26.
27. 28. 29.
793
and infant health; Volume 3: Methodology and documentation. London: The Stationery Office; 2003. Piccinelli M, Wilkinson G. Gender differences in depression. Critical review. Br J Psychiatry 2000;111:486–92. Politi PL, Piccinelli M, Wilkinson G. Reliability, validity and factor structure of the 12-item General Health Questionnaire among young males in Italy. Acta Psychiatr Scand 1994;90:432–7. Statutory Instrument 1999, No. 3312 The Maternity and Parental Leave etc. Regulations. The Stationery Office. London: 1999. Available at:, http://www.opsi. gov.uk/si/si1999/19993312.htm ; [accessed 22 October 2009]. Committee on Medical Aspects of Food. Weaning and the weaning diet. Health and social subjects. London: HMSO; 1994. Lee TS, Yip ASK, Chiu HFK, Chung T. Screening for postnatal depression using the double-test strategy. Psychosom Med 2000;62:258–63. Boyd R, Le H, Somberg R. Review of screening instruments for postpartum depression. Arch Womens Ment Health 2005;8:141–53.
Contents lists available at ScienceDirect
Public Health journal homepage: www.elsevierhealth.com/journals/pubh
Original Research
Comparison of scoring methods and thresholds of the General Health Questionnaire-12 with the Edinburgh Postnatal Depression Scale in English women N.J. Shelton a, *, K.G. Herrick b a b
Department of Epidemiology and Public Health, University College London (UCL), 1–19 Torrington Place, London WC1E 6BT, UK Nutrition and Health Sciences, Emory University, Atlanta, GA 30322, USA
a r t i c l e i n f o
s u m m a r y
Article history: Received 15 May 2009 Received in revised form 8 September 2009 Accepted 22 September 2009 Available online 17 November 2009
Objectives: To compare the scoring methods and thresholds of the 12-item General Health Questionnaire (GHQ-12) and the Edinburgh Postnatal Depression Scale (EPDS) in English women, and to determine which threshold and scoring method provides the closest correlation of caseness of postnatal depression in a nationally representative sample of English women. Study design: Health Survey for England 2002 health examination survey. Methods: Self-completion booklet containing the EPDS and the GHQ-12. Participants were mothers with at least one child under 1 year of age at the time of interview. Results: Both the scoring method and cut-off affected the estimates of prevalence of postnatal depression in English women. The best threshold and scoring method for the GHQ-12 using sensitivity/specificity analysis against the EPDS was a standard scale with a cut-off of 3þ. This matched the cut-off using the GHQ-12 mean scores. The cut-off using comparative prevalence of the GHQ-12 with the EPDS was higher at 4þ. There was a significantly lower estimate of prevalence of postnatal depression at 4 months using the GHQ-12. Conclusions: Care needs to be taken measuring postnatal depression. The GHQ-12 mean score cut-off matched the cut-off using sensitivity and specificity; this supports using the GHQ-12 mean scores as cutoffs. The standard scale was most closely correlated with the EPDS. Although there was strong correlation between the GHQ-12 and the EPDS, a significantly lower proportion of women were measured as having possible postnatal depression at 4 months using the GHQ-12. This may be due to the lack of a question on blame in the GHQ-12. Four months coincided with the duration of maternity leave entitlement and recommended age for weaning in 2002. These events may be particularly stressful for mothers, and practitioners need to be mindful of similar milestones for diagnosis if using the GHQ-12. Ó 2009 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
Keywords: Postpartum depression Postnatal depression GHQ-12 Health Survey for England EPDS
Introduction Postnatal depression can have profound effects on mothers, infants and the wider family. The prevalence of postnatal depression has been estimated at approximately 10% in recently delivered women in the UK,1 and between 10% and 15% internationally.2,3 Correctly identifying postnatal depression is a key concern for healthcare professionals. In the UK, this is usually done by general practitioners or midwives via short questionnaires completed after childbirth. Two commonly used screening instruments in clinical and epidemiological settings are the Edinburgh Postnatal
* Corresponding author. Tel.: þ44 (0)20 7679 5648; fax: þ44 (0)20 7813 0242. E-mail address: [email protected] (N.J. Shelton).
Depression Scale (EPDS) and the General Health Questionnaire (GHQ). The EPDS is a dedicated 10-item postnatal depression screening tool, whilst the GHQ is a 60-item screening tool for nonpsychiatric morbidity, commonly found in shortened versions of 30 (GHQ-30) and 12 (GHQ-12) items. Both the EPDS and the GHQ are currently used to screen for depression. The EPDS, introduced in 1987, was developed as a self-administered tool for use in clinical and research settings to identify mothers at risk of postnatal depression.4,5 The scale is composed of 10 questions that a mother completes by selecting the answer that best describes her feelings over the past 7 days. Each question is given a score; summed, these questions provide an overall score on the instrument. A bimodal threshold exists for the instrument.6 When identifying ‘definite major depression’, the threshold of 12/ 13 is recommended, whereas the threshold of 9/10 is
0033-3506/$ – see front matter Ó 2009 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.puhe.2009.09.012
790
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793
recommended for screening in the community. Timing is also important in the use of the EPDS. Studies have shown that half of all cases of postnatal depression start within the first 3 months and three-quarters within the first 6 months after childbirth 7; therefore, three contact points during which the scale could be administered are recommended. The current suggested times for use are 5–8, 10–14 and 20–26 weeks postnatally. Since its introduction, there have been validation studies in many languages and in populations with varied socio-economic backgrounds.4 It is considered the ‘gold standard’ of self-administered questionnaires and the instrument of choice when the outcome of interest is postnatal depression. The GHQ-12, a shortened version of a 60-item screening tool developed by Goldberg in 1970, is a screening instrument for depression/general non-psychiatric morbidities.8 It comprises 12 questions, six of which are positively phrased and six negatively phrased, with a five-option ‘more/less than usual’ response. Three scoring methods are commonly used. These are the original scale (for absence or presence of condition), and two other less frequently used scales: the Likert and the chronic scales.9 With the Likert scale, each component is scored on a five-point scale relating to severity. On the chronic scale, the response ‘no more than usual’ is considered to be indicative of ill health for the six negatively worded questions and scored. In general clinical settings, higher thresholds may be required to identify cases, as higher GHQ scores are expected as a consequence of symptoms of physical illness.10 The GHQ has been used in many populations and translated into several languages.10–12 It has been claimed that ‘the GHQ-12 can be used and should be preferred in all clinical settings for screening and case detection’ of psychological disorders.13 Its use in postnatal settings has been well documented 14,15; however, this same literature disagrees on the most appropriate threshold and even scoring method. Generally, higher cut-offs are often used in postnatal settings, e.g. 4/513 compared with 1/2 or 2/3 in general populations.10 All of the aforementioned thresholds apply to the most commonly used scoring method, not the Likert or chronic scales. It has also been argued that the GHQ-12 had a broader coverage of neurotic conditions, and so was ‘potentially superior’ to the EPDS and could identify somatic illness.15 Contradictory to these studies, a study examining the case identification properties of the GHQ-12 using three different scoring methods concluded that the GHQ-12 was not recommended to identify psychological distress in postnatal samples.16 The disagreement between these studies highlights a debate that has followed the GHQ since its invention: how does one select the appropriate threshold for the sample of interest? The recommendation from the scale’s author is to carry out a validation study in the population of interest,8 but the associated expense and impracticality is often a deterrent. Thus, in 1998, the GHQ’s author and others recommended an alternative to a validation study; the mean score method to set a crude threshold.17 Martin and Jomeen used this approach in their study of 58 pregnant women and still felt it was inadequate. As the three GHQ-12 scales gave conflicting levels of possible depression, they asserted the notion that the scale should be validated in every setting prior to use; this is not feasible.16 As their study did not use a clinical screening instrument or screening questionnaire for comparison, it is impossible to tell which, if any, of the scales would have been appropriate, or if they should have chosen different cut-offs for each scale. Retrospective significance tests and power calculations based on the small sample size of the Martin and Jomeen paper carried out for this research (results not shown) showed that, despite the differences in prevalence being large (approximately 20%), they were not statistically significant and the power of the study was low. More recently, Navarro et al. argued that both the
EPDS and the GHQ are useful instruments for detecting postnatal psychiatric morbidity.18 To compare postnatal women with the wider population, a more comprehensive scale such as the GHQ-12 in a survey setting may be useful. However, when using the GHQ-12, which threshold and scoring method provides closest correlation of caseness of postnatal depression between the GHQ-12 and the EPDS, and to what extent does the choice of measurement tool, scoring method and cut-off affect the estimates of prevalence of postnatal depression? The EPDS has the advantage that it is shorter (10 questions compared with 12) and therefore cheaper and quicker to deliver, so if postnatal depression is the outcome of interest, it may be the preferred instrument. However, the EPDS is limited to postnatal depression and was not designed to pick up somatic illness.4 Several studies have argued that the EPDS is not only applicable postnatally, but can be suitable for other groups of women19 including pregnant women20 and even new fathers.21,22 There is also debate in the literature regarding the latest point at which postnatal depression can be diagnosed; i.e. when is a diagnosis of depression for women with children no longer a diagnosis of postnatal depression?13 The EPDS authors recommend 6 months. Methods The Health Survey for England (HSE) is an annual survey designed to monitor the health of people living in England, and seeks to inform policy aimed at improving their health. Core statistics are collected each year, and additional modules focus on specific demographic groups or disease conditions in different years. The first survey was conducted in 1991, and the twelfth in the series, the 2002 report (used here), comprised the standard random cluster, cross-section sample designed to be representative of the English population, as well as the inclusion of a new module (Maternal and Infant Health). Further details of the full survey can be found in the HSE 2002 report.23 Ethical approval was obtained from the London Multi-centre Research Ethics Committee. During the interview stage of the survey, mothers were approached at home and asked to fill out a self-completion booklet which contained both the EPDS and the GHQ-12. The inclusion criterion used for the Maternal and infant Health Module was mothers with an infant aged under 1 year at the time of interview (n ¼ 399). Of these, 394 mothers (98.7%) had both valid GHQ-12 scores and EPDS scores. Their demographics were not found to differ significantly from non-responders with regards to age, parity, time since childbirth, social support, occupation of the household reference person, index of multiple deprivation, or lone- or twoparent household (data not shown). Mothers were interviewed at a random time point within the infant’s first year of life; both the GHQ-12 and the EPDS were administered in the same interview. Three scoring methods were used here for responses to the GHQ-12. These were the standard GHQ-12 method (0011 – zeros for positive or neutral response), the Likert type method (0123 – scoring increases with increased negativity of responses) and the chronic method (scores negative questions 0111: zeroes for positive responses only; positive questions 0011: zeroes for positive and neutral responses). Cut-offs were calculated for caseness using two methods: correlation of the GHQ-12 with the EPDS, and the GHQ12 mean score (the mean score in the study population was calculated and this was used as the threshold). Results Table 1 shows the percentage of possible postnatal depression in women using several different scales. The prevalence was 24.4% using the EPDS with community (10þ) threshold. The general,
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793 Table 1 Prevalence of postnatal depression for the Edinburgh Postnatal Depression Scale (EPDS) and different General Health Questionnaire-12 (GHQ-12) cut-offs and scoring methods. GHQ-12 3þ
GHQ-12 4þ
GHQ-12C 6þ
GHQ-12C 7þ
GHQ-12L 14þ
GHQ12L 15þ
24.4
27.9
21.1
34.5
22.3
24.6
20.6
GHQ-12, standard scoring method; GHQ-12C, chronic scoring method; GHQ-12L, Likert-type scoring method.
14 12 10 Mean score
EPDS 10þ
791
EPDS GHQ12-L GHQ12-C GHQ-12
8 6 4 2
Likert and chronic scoring methods were then used with the GHQ12 to estimate the level of possible postnatal depression in the sample. The thresholds for the GHQ-12 were chosen to maximize similarity in the proportion of cases between the GHQ-12 and the EPDS. This identified a threshold of 4/5 for GHQ-12, 7/8 for the chronic scale (GHQ-12C) and 14/15 for the Likert scale (GHQ12-L). In contrast, using the mean scores method led to lower cut-offs: 2/3 for GHQ-12, 4/5 for GHQ-12C and 11/12 for GHQ12-L, and a higher prevalence of caseness than the EPDS. Table 2 shows the sensitivity and specificity of the GHQ-12 compared with the EPDS. Using an average of sensitivity (the proportion of cases correctly identified by test) and specificity (the proportion of non-cases correctly identified by test) for identifying postnatal depression, this test identified 2/3 as the best cut-off for GHQ-12, 3/4 for GHQ-12C and 7/8 for GHQ-12L. Fig. 1 presents mothers’ mean scores for the EPDS and the GHQ-12 scored three different ways by age of infant in months. Looking at the variation in depression by infant age between the different scales in more detail, there was reasonable correlation between the scoring methods over time, except at 4 months when the EPDS showed an upward spike and the GHQ-12 showed a plateau (Fig. 1). This difference was statistically significant (P < 0.000, confidence interval 3.330–0.550, n ¼ 27) and would result in mothers being identified using the EPDS but not the GHQ-12. This difference was not identifiable from the prevalence of postnatal depression at 3–5 months, nor when the prevalences at 4 months were compared, although the sample size was small (data not shown).
Table 2 Performance of General Health Questionnaire-12 (GHQ-12) scales against the Edinburgh Postnatal Depression Scale (EPDS). Cut-off
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
2/3 3/4 4/5
65 59 50
85 92 96
61 74 81
87 86 84
3/4 4/5 5/6
93 88 78
51 64 80
41 48 59
95 93 91
GHQ-12 HSE 2002 Romito et al.13 GHQ-12C HSE 2002 GHQ-12L HSE 2002 Politi et al.25
Piccinelli et al.24
7/8 8/9 9/10 10/11 11/12 12/13 13/14 14/15
98 96 95 90 83 76 67 61
24 40 52 66 76 84 90 93
32 37 43 49 56 63 71 77
97 97 97 94 92 90 88 87
Sensitivity, proportion of cases correctly identified by test; specificity, proportion of non-cases correctly identified by test; positive predictive value, probability of disease when the test is positive; negative predictive value, probability of disease when the test is negative; GHQ-12, standard scoring method; GHQ-12C, chronic scoring method; GHQ-12L, Likert-type scoring method; HSE, Health Survey for England.
0 0
1
2
3
4
5
6
7
8
9
10 11
Age of infant (months) Figure 1. Mothers’ mean scores for the Edinburgh Postnatal Depression Scale (EPDS) and the 12-item General Health Questionnaire (GHQ-12) scored three different ways, by age of infant in months.
These results raised the question of why the two tools might diverge at 4 months. The GHQ-12 is a measure of general psychological morbidity and the EPDS is a specific measure of depression. Table 3 shows a summary of the topics in the two questionnaires. A correlation matrix was calculated comparing negative/positive responses to the GHQ-12 and the EPDS (data not shown). Responses to two questions from the EPDS showed no significant correlation with any items in the GHQ-12. These were self-harm and blame. Given that the EPDS does not include screening questions for somatic illness, it was thought that this might account for the difference in levels of possible depression found. All items in the GHQ-12 were correlated with one or more responses in the EPDS, despite the lack of screening questions for somatic illness in the EPDS. Although there was a fall in the prevalence of feeling blame at 2 months and a rise at 3 and 4 months, the sample sizes were small and the difference was not significant. Discussion Care needs to be taken when choosing a tool (and cut-off and scoring method) for measuring postnatal depression. The three methods of identifying caseness in GHQ-12 used here – comparison of proportion of cases in the sample between the GHQ-12 and the EPDS, average of sensitivity and specificity compared with the EPDS, and using the GHQ-12 mean score as the cut-off – produced different cut-offs for caseness. The standard scale was most closely associated with the EPDS for each method. The GHQ-12 mean score
Table 3 Topics of questions in the General Health Questionnaire-12 (GHQ-12) and the Edinburgh Postnatal Depression Scale (EPDS). Topic
In both questionnaires
Sleep Strain Overcome Enjoy Unhappy Happy Worth Confidence Concentration Face up Useful Blame Scared/panic Fear Self-harm
X Aspects of X X X X
In GHQ-12 only
In EPDS only
X X X X X X X X X
792
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793
produced the same cut-off (3þ) as the sensitivity/specificity analysis, supporting the use of the mean score method for determining cut-offs. The choice of scale and cut-off for the GHQ-12 altered the estimation of possible postnatal depression among women in this study considerably. A priori, it was thought that the most appropriate scoring method and cut-off point for the GHQ-12 to maximize correlation with the EPDS for women who had recently given birth would be one that took chronic pain into account. However, the standard scale corresponded better with the EPDS than the chronic scale in this study for all cut-offs. Prevalence of the EPDS was used as a method of choosing appropriate cut-off points. For the standard GHQ-12 scale, this identified a cut-off of 4þ (which is the same as that recommended by Romito et al. and Navarro et al.)13,18 for postnatal settings, a cut-off of 7þ for the chronic scale (which is 2 more than that recommended in chronic patients) and a cut-off of 14þ for the Likert scale (which corresponds with Piccinelli et al.24 but not Politi et al.25 who recommended 9þ). According to the receiver operating characteristic curve, 4/5 was the optimal cut-off score for the GHQ-12. For the EPDS, the optimal cut-off score was 9/10. Sensitivity and specificity comparisons with the EPDS identified lower cut-offs (3þ for standard scale) and greater prevalence of caseness with the GHQ-12 than the EPDS, as did the GHQ-12 mean scores. The divergence of caseness between the GHQ-12 and the EPDS at 4 months may require understanding of what was happening in the mothers’ lives at the point when the survey was carried out. Those diagnosing depression may need to review mothers’ postnatal mental health in line with major milestones in the mothers’ and infants’ lives. In 2002, statutory maternity leave was 18 weeks in England.26 Four months may have corresponded with mothers returning to work. Also, the recommended age for weaning an infant was 4 months in 2002,27 which may correspond with a particularly stressful time for the mother. The significantly lower proportion of women measured as having postnatal depression at 4 months using the GHQ-12 compared with the EPDS may be due to inclusion of questions on blame in the EPDS. Milestones in the mother’s life or the infant’s first year may have been the trigger for the higher level of postnatal depression seen in women with infants of this age. Clinicians need to consider that postnatal depression is not necessarily something that starts almost immediately after birth. Screening around these major milestones may be required, and these may vary from woman to woman and change over time with changes in postnatal policies such as maternity leave allowances etc. The EPDS and the GHQ-12 shared many common factors; despite the absence of somatic screening questions in the EPDS, there was significant correlation between all of the GHQ-12 questions and the EPDS questions. The two factors in the EPDS which were not correlated with any questions in the GHQ-12 were blame and self-harm. Lee et al.28 has argued that the best method of identifying postnatal depression using short screening tools is the ‘Double test strategy’, where components of the GHQ-12 are appended to the EPDS. The GHQ-12 offers the opportunity to compare levels of depression in postnatal women with that in other groups. In a clinical setting, false negatives must be reduced at the expense of false positives. The level of false positives compared with false negatives is not as important in survey data, but the magnitude of the error should be small in a survey setting. Some studies argue that the GHQ-12 is a suitable tool for screening and measuring the prevalence of postnatal depression, while others do not. In a review of postpartum depression screening instruments, Boyd et al.29 argued that given the lack of consensus about the utility and psychometric properties of screening measures in both clinical and research settings,
additional research is needed to determine the best measure for large-scale screening efforts for postpartum depression. In addition, this study shows that choice of cut-offs significantly affects estimates of the prevalence of depression, as does the scale type (standard, Likert, chronic). These must also be considered when choosing a method. Using the GHQ-12 mean score method produced a higher estimation of prevalence of postnatal depression than the EPDS, but the closest relationship with sensitivity and specificity supporting its use for determining cut-offs. The limitations of this study were that it had no clinical comparison. A larger sample size would be required to test the relationship between increased EPDS scores at 4 months but not GHQ-12 scores, and questions on blame in the EPDS and not the GHQ-12. Acknowledgements The authors wish to thank Paola Zaninotto, University College London, for advice with statistical analyses, and the anonymous referees for their comments. The authors are grateful to the participants in the Health Survey for England, the field staff and colleagues at the National Centre for Social Research. Ethical approval London Multi-centre Research Ethics Committee. Funding Kirsten Herrick was funded by the Department of Health as part of the team to carry out the Health Surveys for England, but these analyses have been conducted independently of the funders. The views expressed in this paper are those of the authors, not the funding bodies. References 1. MacArthur C, Lewis M, Knox E. Health after childbirth. London: HMSO; 1991. 2. O’Hara MW, Swain AM. Rates and risk of postpartum depression – a metaanalysis. Int Rev Psychiatry 1996;8:37–54. 3. Lee DTS, Yip SK, Chiu HFK, Leung TYS, Chan KPM, Chau IOL, et al. Detecting postnatal depression in Chinese women. Validation of the Chinese version of the Edinburgh Postnatal Depression Scale. Br J Psychiatry 1998;172:433–7. 4. Cox JL, Holden JM, editors. Perinatal psychiatry: use and misuse of the Edinburgh Postnatal Depression Scale. London: Gaskell; 1994. 5. Cox JL, Holden JM, Sagovsky R. Detection of postnatal depression development of the 10-item Edinburgh postnatal depression scale. BMJ 1987;150:782–6. 6. Goodman JH. Paternal postpartum depression, its relationship to maternal postpartum depression, and implications for family health. J Adv Nurs 2004;45:26–35. 7. Cooper PJ, Campbell EA, Day A, Kennerly H, Bond A. Non-psychotic psychiatric disorder after childbirth: a prospective study of prevalence, incidence, course and nature. Br J Psychiatry 1988;152:799–806. 8. Goldberg D. Manual of the General Health Questionnaire. Windsor: NFER-Nelson; 1978. 9. Goodchild ME, Duncan-Jones P. Chronicity and the General Health Questionnaire. Br J Psychiatry 1985;46:55–61. 10. Goldberg DP, Williams P. The user’s guide to the General Health Questionnaire. Windsor: NFER-Nelson; 1988. 11. Nott PN, Cutts A. Validation of the 30-item General Health Questionnaire in postpartum women. Psychol Med 1982;12:409–13. 12. Jacob S, Bhurgra D, Mann AH. The validation of the 12-item General Health Questionnaire among ethnic Indian women living in the United Kingdom. Psychol Med 1997;27:1215–7. 13. Romito P, Saurel-Cubizolles MJ, Lelong N. What makes new mothers unhappy: psychological distress one year after birth in Italy and France. Soc Sci Med 1999;49:1651–61. 14. Werneke U, Goldberg DP, Yalcin I, Ustu¨n BT. The stability of the factor structure of the General Health Questionnaire. Psychol Med 2000;30:823–9. 15. Lee DTS, Yip ASK, Chiu HFK, Leung TYS, Chung TKH. Screening for postnatal depression: are specific instruments mandatory? J Affect Disord 2001;63:233–8. 16. Martin CR, Jomeen J. Is the 12-item General Health Questionnaire (GHQ-12) confounded by scoring methods during pregnancy and following birth? J Reprod Infant Psychol 2003;21:267–78.
N.J. Shelton, K.G. Herrick / Public Health 123 (2009) 789–793 17. Goldberg DP, Oldehinkel T, Ormel J. Why GHQ threshold varies from one place to another. Psychol Med 1998;28:915–21. 18. Navarro P, Ascaso C, Garcia-Esteve L, Aguado J, Torres A, Martı´n-Santos R. Postnatal psychiatric morbidity: a validation study of the GHQ-12 and the EPDS as screening tools. Gen Hosp Psychiatry 2007;29:1–7. 19. Cox JL, Chapman G, Murray D, Jones P. Validation of the Edinburgh Postnatal Depression scale (EPDS) in non-postnatal women. J Affect Disord 1996;39:185–9. 20. Murray D, Cox JL. Screening for depression during pregnancy with the Edinburgh Depression Scale (EPDS). J Reprod Infant Psychol 1990;8:99–107. 21. Matthey S, Barnett B, Kavanagh DJ, Howie P. Validation of the Edinburgh Postnatal Depression Scale for men, and comparison of item endorsement with their partners. J Affect Disord 2001;64:175–84. 22. Madsen SA, Juhl T. Paternal depression in the postnatal period assessed with traditional and male depression scales. J Mens Health Gend 2007;4:26–31. 23. Sproston K, Primatesta P. Health Survey for England 2002. Summary of key findings. Volume 1: The health of children and young people; Volume 2: Maternal
24. 25.
26.
27. 28. 29.
793
and infant health; Volume 3: Methodology and documentation. London: The Stationery Office; 2003. Piccinelli M, Wilkinson G. Gender differences in depression. Critical review. Br J Psychiatry 2000;111:486–92. Politi PL, Piccinelli M, Wilkinson G. Reliability, validity and factor structure of the 12-item General Health Questionnaire among young males in Italy. Acta Psychiatr Scand 1994;90:432–7. Statutory Instrument 1999, No. 3312 The Maternity and Parental Leave etc. Regulations. The Stationery Office. London: 1999. Available at:, http://www.opsi. gov.uk/si/si1999/19993312.htm ; [accessed 22 October 2009]. Committee on Medical Aspects of Food. Weaning and the weaning diet. Health and social subjects. London: HMSO; 1994. Lee TS, Yip ASK, Chiu HFK, Chung T. Screening for postnatal depression using the double-test strategy. Psychosom Med 2000;62:258–63. Boyd R, Le H, Somberg R. Review of screening instruments for postpartum depression. Arch Womens Ment Health 2005;8:141–53.