Depressive disorders are leading contributors to burden of disease in developing countries. Research aiming to improve their diagnosis and treatment is fundamental in these settings, and psychometric tools are widely used instruments to support mental health research. Our aim is to validate and compare the psychometric properties of the Spanish versions of the Center for Epidemiological Studies Depression Scale (CES-D) and the Zung Self-Rating Depression Scale (ZSDS).
A Spanish version of the CES-D was revised by 5 native Spanish speaking psychiatrists using as reference the English version. A locally standardized Spanish version of the ZSDS was used. These Spanish versions were administered to 70 patients with a clinical diagnosis of DSM-IV Major Depressive Episode (MDE), 63 without major depression but with clinical diagnosis of other psychiatric disorders (OPD), and 61 with no evidence of psychiatric disorders (NEP). For both scales, Cronbach's alpha (C-α) and Hierarchical McDonald Omega for polychoric variables (MD-Ω) were estimated; and receiver operating characteristics (ROC) analysis performed. For the CES-D and ZSDS scales, C-α was 0.93 and 0.89 respectively, while MD-Ω was 0.90 and 0.75 respectively. The area under the ROC curve in MDE+OPD was 0.83 for CES-D and 0.84 for ZSDS; and in MDE+NEP was 0.98 for CES-D and 0.96 for ZSDS. Cut-off scores (co) for the highest proportions of correctly classified (cc) individuals among MDE+OPD were ≥29 for CES-D (sensitivity (ss) = 77.1/specificity (sp) = 79.4%/(cc) = 78.2%) and ≥47 for ZSDS (ss = 85.7%/sp = 71.4%/cc = 78.9%). In the MDE+NEP, co were ≥24 for the CES-D (ss = 91.4%/sp = 96.7%/cc = 93.9%) and ≥45 for the ZSDS (ss = 91.4%/sp = 91.8%/cc = 91.6%).
Citation: Ruiz-Grosso P, Loret de Mola C, Vega-Dienstmaier JM, Arevalo JM, Chavez K, Vilela A, et al. (2012) Validation of the Spanish Center for Epidemiological Studies Depression and Zung Self-Rating Depression Scales: A Comparative Validation Study. PLoS ONE 7(10): e45413. https://doi.org/10.1371/journal.pone.0045413
Editor: Leonardo Fontenelle, Institute of Psychiatry at the Federal University of Rio de Janeiro, Brazil
Received: January 12, 2012; Accepted: August 22, 2012; Published: October 8, 2012
Copyright: © Ruiz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: These authors have no support or funding to report.
Competing interests: The authors have declared that no competing interests exist.
Globally, unipolar depression is a major contributor of burden of disease, and its impact is growing , . Also, research studies regarding risk factors, treatment, and associations of depressive disorders with other chronic and acute diseases show an increase on the importance of these mental disorders in global health and their harmful effect on people's health –.
Depression scales such as the Beck Depression Inventory (BDI) , the Center for Epidemiologic Studies Depression Scale (CES-D) , the Zung Self-Rating Depression Scale (ZSDS) , and the Patient Health Questionnaire (PHQ) ,  are widely used as depression screening tools for both diagnosis support and research. Recent meta-analytic studies report a similar performance in discriminative properties of the Hospital Anxiety and Depression Scale (HADS) (cut off score (co) ≥8; sensitivity (ss) = 0.82; specificity (sp) = 0.74) and of the Geriatric Depression Scale (GDS) (ss = 0.92; sp = 0.77) , . A meta-analysis of Hamilton Rating Scale for Depression (HRSD), which is one of the most widely used, revealed that the intra class correlation coefficient was 0.94, the kappa coefficient 0.81, and the Pearson correlation coefficient 0.94 . Current evidence suggests that there are no differences between them as screening tools for major depression  and their scores have showed good correlation .
The performance of various scales aiming to screen for depressive disorders has been reported with good results in Spanish language, including Latin America. For example, the Depressive Psychopathology Scale (DPS) reported good internal consistency (Cronbach's alpha (C-α) = 0.86) and discriminative power (ss = 77.7% and sp = 72.3) for the detection of major depressive disorder in a sample of Peruvian patients attending the National Institute of Mental Health . Both 5 and 15 item versions of the GDS showed good psychometric properties in Spanish elderly (ss = 86.4/81.8%; 85.6/97.7%) , as well as an custom questionnaire for the elderly used in Mexico (C-α = 0.74; co≥5; ss = 80.7%, sp = 68.7%)  and the Edinburgh Postpartum Depression Scale (EPDS) in Puerperal Mexican Woman (C-α = 0.75; area under receiver operating characteristics curve (auROC) = 0.80, co≥7; ss = 75%; sp = 84%) .
In other Spanish speaking settings outside Latin America, the PHQ-15 showed a good internal consistency (C-α = 0.78), as did the GDS, when used in visually impaired individuals (C-α = 0.91) and the Postpartum Depression Screening Scale (C-α = 0.97) –. Adequate internal consistency and discriminative properties were reported for the World Health Organization Disability Assessment Schedule II (WHO-DAS II) (co≥50; ss = 71.4%; sp = 67.6%; proportion of correctly classified individuals (cc) = 70.4%)  and for the Euro-D in Spanish elderly (C-α = 0.75; area under the ROC curve auROC = 0.92, co≥3; ss = 91.8%; sp = 76.6%) .
The CES-D was found to be reliable in detecting depressive symptoms in Puerto Rican elderly with cognitive impairment (auROC = 0.90) , Colombian university students (C-α = 0.88) , adolescents from a sample of general population during a validation of short versions of 10 and 3 items (C-α = 0.86/0.74; auROC = 0.83/0.80; ss = 77.8/77.6% and sp = 74.1/70.7%)  and full scale (C-α = 0.85; auROC = 0.82; co≥23; ss = 73.3%; sp = 73.6%) . Also, good internal consistency (C-α = 0.93) was found in Mexican adolescents of middle school . In Spain, the CES-D was validated on a sample of patients with mood disorders (co≥16; ss = 95%; sp = 91%)  and non-psychiatric population (C-α = 0.89; co≥26; ss = 90.6%; sp = 91.8%) . A 10 item version of the ZSDS was validated in Colombian general population (C-α = 0.80; ss = 95.5%; sp = 70.3%)  and in Spanish primary care patients (ss = 95%; sp = 74%) . Finally in general population from Puerto Rico the ZSDS showed good internal consistency (C-α = 0.85) .
In 2009, Reuland et al reviewed the diagnostic accuracy of Spanish language depression screening instruments. Only, three studies from non-US Spanish were selected by the authors based on quality appraisal (EDPS, MHAS and PHQ-9). The overall conclusion was that, based on their review (including US-based validations), the CES-D and the PRIME-MD-9 might be useful for detecting depressed patients in primary care on the United States of America. Despite this, there was little evidence on primary care performance of depression scales in non-US Spanish speakers .
The availability of free to use, valid instruments might encourage independent research initiatives addressing the diagnosis, treatment and prevention of MDE in low and middle income countries, as well as contribute to alleviate the under diagnosis of depressive disorders in primary care . Besides the DPS, which have showed to be appropriate for the discrimination of MDE on a population with a high prevalence of psychiatric disorders, such as the Peruvian National Institute of Mental Health population, few studies have studied the psychometric properties of depression screening scales in general hospital settings.
Both the CES-D and ZSDS scales have already been validated on university and middle school adolescents, elderly and general population in countries of Latin America; however, we could not find studies that specifically validated these scales on general hospital settings. We choose to validate the CES-D and ZSDS scales as both of them have already been validated in Latin America, their use poses no cost for researchers and there is evidence supporting their use albeit at different settings , , , . This study aimed to evaluate the internal consistency and validity of an adapted Spanish version of the CES-D and ZSDS scales for the detection of Major Depressive Episode (MDE) using the diagnosis of a psychiatrist as defined by DSM-IV criteria as reference, and to compare the psychometric properties of the adapted scales.
This study aimed to estimate the internal consistency and cutoff points for a maximum number of persons correctly classified as well as highest sensitivity and specificity of the CES-D and ZSDS on a sample of participants with clinical diagnosis of MDE, other mental disorders and persons without evidence of mental disorders on waiting room of a public hospital in a developing country. Discriminative properties of both scales are also compared.
All of the patients who were waiting for services at the psychiatric and internal medicine outpatient consultations at the “Hospital Nacional Cayetano Heredia” (HNCH) from January to December 2006 were invited to participate in the study. The HNCH is a third level public hospital that serves three of the most populated districts in the northern part of Lima. Mental health care in Peru is usually provided in the psychiatry outpatient consultation areas in hospitals like HNCH. All patients who participated spoke Spanish as their native language. Patients attending HNCH are usually of low socio-economic status and participants were between 18 and 65 years of age. In terms of the groups of participants, those recruited from the psychiatry consultation included 70 people with Major Depressive Episode (MDE) and 63 people with other DSM-IV diagnostics (OPD), and those recruited from the internal medicine outpatient consultation included 61 people with no evidence of psychiatric disorders (NEP). Consecutive patients on the waiting room of the psychiatry and internal medicine consultation were invited to participate in the study until the calculated sample size for the study was achieved. Everyone gave informed consent prior to initiating participation. MDE diagnosis by a psychiatrist using DSM-IV criteria was an inclusion criterion for the MDE group, while the DSM-IV diagnosis of other psychiatric disorders but not MDE by the same psychiatrists was a criterion for the OPD group. We ruled out major depressive episode in the NEP group using the DSM-IV Structured Clinical Interview for Major Depression (SCID-I), and excluded those that resulted positive for MDE. We also excluded patients with physical or mental pathologies that could prevent them from completing the psychometric tests. Literacy was checked as part of the informed consent process by the investigators.
For the sample size calculation, a sensitivity and specificity of 80% was assumed, and the minimal acceptable value was 70% for both. To calculate the sensitivity and specificity with a confidence interval of +/−10 and a probability of Type I error of 5%, we needed to recruit at least 61 participants in each group (MDE, OPD and NEP).
A cross sectional design was used to establish the validity, internal consistency, and psychometric differences of the Spanish versions of CES-D and the ZSDS. Three groups of participants were established, one with no evidence of psychiatric disorders (“NEP” group), one with major depressive episode (“MDE” group), and the other without major depressive episode but with any other psychiatric disorder (“OPD” group). A sample of outpatients from the psychiatric and internal medicine consultations from the Hospital Nacional Cayetano Heredia (HNCH) in Lima, Peru was used to establish these groups.
All of the groups of participants completed the pen and paper versions of the CES-D and ZSDS while on the waiting room of medicine or psychiatry outpatient consultation, and their socio-demographic data was also registered by the investigators. The psychiatric diagnosis, based on the DSM-IV classification, any other medical disease, and the Clinical Global Impression- Severity Scale (CGI-S) were made and registered by the medical assistant in charge of the consulting room, except in the NEP group where no CGI-S values were recorded.
The CES-D is a 20-item scale designed to be a case-detection instrument for depressive disorders in the general population. It has been validated in several languages, including Spanish , , , and in a wide range of populations, including adolescents – and elderly people –. Previous studies support the use of CES-D as a good psychometric test in cross-cultural contexts such as Latin America . The CES-D is composed of 20 items; each one scored in a scale from “0” to “3” according to the amount of days on the previous days that the person felt according to the item's premise, thus the total score varies from 0 to 60.
The ZSDS is also a 20-item scale to help physicians in primary care settings to identify depressive symptoms , . The ZSDS has been validated and its factor structure analyzed in different languages – and in diverse specific populations such as oncology patients , people with cognitive impairment  and Parkinson's disease , and college and university students , . The ZSDS is also composed of 20 items, each one with punctuation from 1 to 4, making the range of the completed scale range from 20 to 80.
The CES-D scale used was the Spanish online version from the Center of Epidemiological Studies adapted by the Patient Education Center from the Medical School of Stanford University. It was revised by a group of 5 native Spanish speaker psychiatrists having as reference the English version provided by the same organization and a consensus version was reached. The psychiatrists suggested a few minor changes in the use of some words. The used ZSDS version corresponds to a standardized revised version used by the Peruvian National Mental Health Institute (PNMHI) in Lima.
Statistically significant differences in age, educational level, gender and scores on the CGI, CES-D and ZSDS were analyzed across the MDE, OPD and NEP groups using a non-parametric test (Kruskall Wallis test and Spearman's rank correlation coefficient, “Rho”) since the data did not fulfill the normality assumption for the use of parametrical tests. Sensitivity and specificity were assessed for each scale independently using ROC curves, and the best cut-off points were determined using the score with the highest percentage of correctly classified individuals.
We also examined statistically significant differences in the area under the ROC curve between the CES-D and the ZSDS. ROC curve analyses were performed using the MDE versus the NEP (MDE+NEP), and then MDE versus the OPD (MDE+OPD). Differences between ROC curves were performed using a two sided hypothesis test of equality of the auROC (“roccomp” command of STATA V.10). Internal consistency analyses were performed using the C-α and hierarchical McDonald's Omega coefficient using maximum likelihood estimation for polychoric variables . Confidence intervals (CI) were calculated at 95% and a p value <0.05 was considered significant. The software STATA, version 10, was used for all statistical analyses, except for the estimation of the McDonald's Omega coefficient MD, for which the R statistical software version 2.15.1 was used.
A total of 194 participants were recruited, 70 for the MDE, 63 for OPD and 61 for the NEP group. Only three potential participants on the NEP group refused to participate in the study. Among OPD participants, 22 received a DSM-IV diagnosis of any anxiety disorder, 15 of any psychotic disorder, 17 any mood disorder different than MDE, 3 were diagnosed with any substance use disorder and 6 other DSM-IV diagnoses.
Comparison of age, gender, educational level as well as CGI, CES-D and ZSDS median scores between groups are shown in Table 1. We found statistically significant differences regarding the proportion of women in the depression group and in the severity of symptoms according to the CGI-S and the CES-D and ZSDS scores. The proportion of women was significantly higher in the MDE group than in the OPD and NEP groups (p<0.01) while the scores on the CES-D and ZSDS were also significantly higher (p<0.01) in the MDE than in the OPD and NEP groups. The median of both CES-D and ZSDS on the MDE group (35.5 & 53.5) was statistically different (p<0.01) than on the OPD (20 & 40) and NEP (9 & 33). CGI-S scores were found to be significantly different (p<0.01) between MDE (p50: 4, p25: 4, p75: 5) and OPD (p50: 4, p25: 4, p75: 5) groups.
For the CES-D and ZSDS scales, C-α was 0.93 and 0.89 respectively. Inter-item covariance, item-test and item-rest correlation as well as the alpha change in the absence of each item for both scales, as shown in Table 2. For CES-D Item-test correlation varied from 0.36 (item 4) to 0.3 (item 18), item-rest correlation ranged from 0.29 to 0.81, while the average inter-item covariance from 0.50 to 0.45, with the items 18 and 4 being the best and worst in performance; C-α would drop from 0.93 to 0.92 if items 6 and 18 would be removed. In the ZSDS, item-test correlation varied from 0.18 to 0.77, item-rest correlation from 0.10 to 0.73, average inter-item covariance from 0.26 to 0.30, with item 18 being having the most favorable estimates and item 2 the poorest performance; C-α would improve from 0.89 to 0.90 if item 2 would be retired. Hierarchical McDonald's Omega coefficients were estimated to be 0.90 and 0.75 for the CES-D and ZSDS respectively.
In the MDE+OPD, the auROC was 0.83 (95% Confidence Interval (CI): 0.76–0.90) for the CES-D and 0.84 (95% CI: 0.76–0.91) for the ZSDS (Figure 1). When we compared the MDE+NEP, the area under the curve was 0.98 (95% CI: 0.97–0.99) for the CES-D and 0.96 (95% CI: 0.93–0.99) for the ZSDS (Figure 2). The CES-D and ZSDS showed good sensitivity and specificity; however the best cut-off scores for the MDE+OPD were higher for both the CES-D (≥29) and ZSDS (≥47), when compared with the cut-off points for the MDE+NEP (≥24 and ≥45, respectively; see Tables 3 and 4).
No statistically significant differences were found between the area under the ROC curve in the CES-D and ZSDS for the MDE+OPD (p = 0.94) or the MDE+NEP (p = 0.14) groups.
We also found a good correlation between the ZSDS and CES-D scores (rho = 0.86, p<0.001), and a statistically significant correlation was also found between the CES-D and CGI scores (rho = 0.51, p<0.001), as well as for the ZSDS and CGI scores (rho = 0.50, p<0.001).
We studied the psychometric properties of the ZSDS and CES-D in two contexts, one in which we analyzed the performance of the scales in a general hospital population (MDE+NEP) and one in which major depression has to be detected in a setting with high prevalence of other psychiatric disorders (MDE+OPD).
Internal Consistency and Discriminant Validity
Cronbach's Alpha results for both scales (CES-D = 0.93, ZSDS = 0.89) were consistent with reports for the CES-D both in a Spanish-language study in a population with affective disorders (0.90)  and also with the internal consistency of the DPS (0.86) which was validated on the PNMHI, with a similar population . Studies with non-general hospital or specialized health care center report internal consistency estimations ranging from 0.85 to 0.93 for the CES-D in Spain , , 0.80 for a 10 item Colombian version of the ZSDS and 0.85 for the full scale in Puerto Rico general population , . The McDonald's Omega coefficient (CES-D = 0.90, ZSDS = 0.75) has been proposed as a more appropriate alternative to Cronbach's Alpha as index of how items on an instrument measure the same latent variable , ; however, the availability of literature to compare the performance of the studied scales in different settings is limited.
On the MDE+OPD group comparisons, sensitivity and specificity (∼80%) was below the results reported by Soler et al (ss and sp ∼90%) and a little above to the findings on the DPS validation (ss ∼77%; sp ∼72%) when using the clinical diagnosis of a psychiatrists as gold standard , . The difference found with the study of Soler et al, might be the result of the use of a different gold standard, in this case the HRSD. On the MDE+NEP group, sensitivity and specificity for both scales was ∼92%, which appears to be slightly above the findings on other Latin America studies in general population for both the CES-D and the ZSDS (ss = 73–95.5%, sp = 70.7–70.4%) –, , .
In previous studies including non-Spanish validations, the recommended cut-off score for the CES-D has varied among populations, from ≥12 to ≥21 for clinically significant depressive symptoms – and from ≥23 to 26 for major depression , , , . As the clinical assessment by psychiatrists according to DSM-IV criteria was considered the gold standard for MDE diagnosis, our results (co≥24) are fairly consistent. For the ZSDS, the best cut-off score (co≥45) was similar to the results for the Greek validation of the ZSDS . The recommended cut-off scores for the MDE+OPD groups were higher (CES-D: ≥29; ZSDS; ≥47) and with lower sensitivity and specificity than the ones for the MDE+NEP groups (Tables 3 and 4).
No statistical differences (p<0.05) were found in the area under the ROC curve comparison between the CES-D and the ZSDS in the MDE+NEP or the MDE+OPD groups. These findings suggest that both scales could have the same predictability of depression between the studied groups, and are valid and consistent psychometric tools in both a general hospital and high prevalence of mental disorders settings, although discriminative properties seems to be diminished for the latter group, as discussed below.
Variation of discriminative properties in non-population settings
Evidence suggests that comorbidity with pathologies with symptoms similar or related to depressive syndromes might affect the performance of psychometric instruments. In studies with patients suffering of rheumatoid arthritis, seven items (items number 2, 4, 8, 11, 12, 16 and 18) had to be removed from the CES-D to reach a good fit for the scale; once retired, the 13 item scale showed a ss = 89.6% and sp = 95.8%, with a co≥9 . The influence of somatic components affecting rheumatoid arthritis, regardless of presenting or not MDE was also supported by Callahan et al . In another study that compared depressive symptoms using the ZSDS in a group of patients with chronic pain and patients from psychology service with comparable depressive symptoms, chronic patients endorsed items referring to psychomotor retardation, sleep disturbance, constipation and fatigue, and thus, might overestimate the depressive symptoms in a similar sample . In a sample of patients suffering from multiple sclerosis, the cut-off score of 16 on the CES-D, which is recommended as cut-off score for detection of clinically significant depressive symptoms, yielded low positive predictive values both for any depressive disorder (74.5%) and major depressive disorder (59.6%), thus suggesting that the score used for general population might not be appropriate for this particular setting . These studies suggest that somatic symptoms that present similitudes to those characteristic of depressive disorders might have a negative effect on the performance of both scales, and also increase their optimal the cut-off scores. Taking this into account, symptoms common with major depression found in various psychiatric disorders could diminish the discriminate properties of the scales, as evidenced by the similar findings of discriminative properties of CES-D and ZSDS described in this study and the DPS validation, which found similar values in similar, even if not identical settings .
The main limitation for this study was that the gold standard for the diagnosis of major depression was not a standardized interview but clinical diagnosis by a psychiatrist. Further, the inter observer concordance for the clinical DSM-IV based diagnosis could not be assessed. This and the possible re-arrangement of items for a high prevalence of mental disorder settings should be engaged in future studies. The results of this study cannot be generalized to other samples that do not meet the conditions and characteristics of this specific setting.
With respect to the use of gold standard, Vega-Dienstmaier et al used both a clinical interview (SCID) and clinical diagnosis of a psychiatrist as gold standard for the validation of the DPS. The auROC was slightly higher when using the SCID as gold standard (0.87 vs. 0.83); the same was true for sensitivity (81.3% vs. 77.7%) and specificity (80% vs. 72.3%). The optimal cut-off score was 1 point lower when using the clinical diagnosis as gold standard (≥27 vs. ≥26) . While the psychometric estimates appear to favor the SCID, the study does not report if this difference is statistically significant different, particularly in the auROC for both assessments. In general, studies validating Spanish versions of depression screening instruments used as gold standards structured interviews , , clinical diagnosis of MDE , , or both . The most reasonably approach might be to collect information of both clinical and structured interview based diagnosis during future evaluations of psychometric tools.
While the psychometric properties of both CES-D and ZSDS in the MDE+OPD group appears to be different than reported performance on general population settings; on the MDE and NEP group, both cut-off score and discriminant properties appears to be congruent with estimates calculated based on general population data.
Use of Results and Further Studies
The availability of validated screening instruments such as the CES-D and ZSDS might represent an important contribution to both research and screening of MDE. This becomes especially important if we take into account that an important amount of sub-diagnosis of depressive disorders in primary care settings of developing countries has been reported  and that very limited resources for independent research have been identified as obstacles to proper mental health policies supported by solid scientific evidence , . The amount of reported interventions focusing on prevention, treatment and rehabilitation of important contributors to burden of disease, such as depressive disorders, are still scarce in Latin America . We expect that the availability of free to use instruments will encourage independent research focused on depressive disorders, as interventions designed in more developed countries might not be useful in Latin American or other developing settings .
Factor structure, test-retest reliability and general population estimates of the psychometric properties of both CES-D and ZSDS might be considered as target for research. Alternative forms of these instruments, such as shorter, telephone or online versions might also be useful in facilitating independent research in developing countries.
We conclude that both CES-D and ZSDS are reliable and consistent instruments for detection of MDE in psychiatric and general hospital settings.
We want to show our gratitude to the psychiatry consultation patients and staff from the Hospital Nacional Cayetano Heredia, for their patience and time that supported this research, especially to Dr. Hever Kruger. We also acknowledge Dr. Angela Bayer and Dr. Rosa María Castillo for their support on the preparation of the manuscript. Finally we wish to thank the medical students on their sixth year (medical externship) from the Universidad Peruana Cayetano Heredia who contributed during data collection.
Conceived and designed the experiments: PRG CLM JMV. Performed the experiments: PRG CLM JMA. Analyzed the data: PRG JMV. Contributed reagents/materials/analysis tools: PRG JMV CLM. Wrote the paper: PRG CLM JMV KC AV ML JH.
- 1. WHO (2001) Mental Health: New Understanding, New Hope. World Health Organization.
- 2. Mathers C, Fat DM, Organization WH, Boerma JT (2008) The Global Burden of Disease: 2004 Update: World Health Organization.
- 3. Steptoe A, Brydon L (2009) Emotional triggering of cardiac events. Neurosci Biobehav Rev 33: 63–70.
- 4. Davidson KW (2008) Emotional predictors and behavioral triggers of acute coronary syndrome. Cleve Clin J Med 75 Suppl 2: S15–19.
- 5. Guarneri E, Horrigan BJ, Pechura CM (2010) The efficacy and cost effectiveness of integrative medicine: a review of the medical and corporate literature. Explore (NY) 6: 308–312.
- 6. Beck AT, Ward CH, Mendelson M, Mock J, Erbaugh J (1961) An inventory for measuring depression. Arch Gen Psychiatry 4: 561–571.
- 7. Radloff LS (1977) The CES-D scale: A self report depression scale for research in the general population. Applied Psychological Measurement 385: 401.
- 8. Zung WW (1965) A Self-Rating Depression Scale. Arch Gen Psychiatry 12: 63–70.
- 9. Kroenke K, Spitzer RL, Williams JB (2001) The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med 16: 606–613.
- 10. Spitzer RL, Kroenke K, Williams JB (1999) Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. Primary Care Evaluation of Mental Disorders. Patient Health Questionnaire. JAMA 282: 1737–1744.
- 11. Brennan C, Worrall-Davies A, McMillan D, Gilbody S, House A (2010) The Hospital Anxiety and Depression Scale: a diagnostic meta-analysis of case-finding ability. J Psychosom Res 69: 371–378.
- 12. Mitchell AJ, Bird V, Rizzo M, Meader N (2010) Which version of the geriatric depression scale is most useful in medical settings and nursing homes? Diagnostic validity meta-analysis. Am J Geriatr Psychiatry 18: 1066–1077.
- 13. Trajkovic G, Starcevic V, Latas M, Lestarevic M, Ille T, et al. (2011) Reliability of the Hamilton Rating Scale for Depression: a meta-analysis over a period of 49 years. Psychiatry Res 189: 1–9.
- 14. Mulrow CD, Williams JW Jr, Gerety MB, Ramirez G, Montiel OM, et al. (1995) Case-finding instruments for depression in primary care settings. Ann Intern Med 122: 913–921.
- 15. Wilcox H, Field T, Prodromidis M, Scafidi F (1998) Correlations between the BDI and CES-D in a sample of adolescent mothers. Adolescence 33: 565–574.
- 16. Vega-Dienstmaier JM, Stucchi-Portocarrero S, Valdez-Huarcaya N, Cabra-Bravo M, Zapata-Vega MI (2011) The Depressive Psychopathology Scale: presentation and initial validation in a sample of Peruvian psychiatric patients. Rev Panam Salud Publica 30: 317–326.
- 17. Ortega Orcos R, Salinero Fort MA, Kazemzadeh Khajoui A, Vidal Aparicio S, de Dios del Valle R (2007) Validation of 5 and 15 items Spanish version of the geriatric depression scale in elderly subjects in primary health care setting. Rev Clin Esp 207: 559–562.
- 18. Aguilar-Navarro SG, Fuentes-Cantu A, Avila-Funes JA, Garcia-Mayo EJ (2007) Validity and reliability of the screening questionnaire for geriatric depression used in the Mexican Health and Age Study. Salud Publica Mex 49: 256–262.
- 19. Alvarado-Esquivel C, Sifuentes-Alvarez A, Salas-Martinez C, Martinez-Garcia S (2006) Validation of the Edinburgh Postpartum Depression Scale in a population of puerperal women in Mexico. Clin Pract Epidemiol Ment Health 2: 33.
- 20. Le HN, Perry DF, Ortiz G (2010) The Postpartum Depression Screening Scale-Spanish version: examining the psychometric properties and prevalence of risk for postpartum depression. J Immigr Minor Health 12: 249–258.
- 21. Ferrando Piera PJ, Pallero R, Anguiano-Carrasco C, Montorio I (2010) Assessment of depressive symptoms in old visually-impaired people: a study of the Geriatric Depression Scale. Psicothema 22: 587–592.
- 22. Luciano JV, Ayuso-Mateos JL, Fernandez A, Aguado J, Serrano-Blanco A, et al. (2010) Utility of the twelve-item World Health Organization Disability Assessment Schedule II (WHO-DAS II) for discriminating depression “caseness” and severity in Spanish primary care patients. Qual Life Res 19: 97–101.
- 23. Larraga L, Saz P, Dewey ME, Marcos G, Lobo A (2006) Validation of the Spanish version of the EURO-D scale: an instrument for detecting depression in older people. Int J Geriatr Psychiatry 21: 1199–1205.
- 24. Ros L, Latorre JM, Aguilar MJ, Serrano JP, Navarro B, et al. (2011) Factor structure and psychometric properties of the center for epidemiologic studies depression scale (CES-D) in older populations with and without cognitive impairment. Int J Aging Hum Dev 72: 83–110.
- 25. Galvis FH (2010) Factorial structure and psychometric properties of a scale for depression among university students in Colombia. Rev Panam Salud Publica 27: 110–116.
- 26. Rueda-Jaimes GE, Camacho Lopez PA, Rangel-Martinez-Villalba AM (2009) Validation of two short versions of the Centre for Epidemiological Studies Depression Scale in Colombian adolescents. Aten Primaria 41: 255–261.
- 27. Camacho PA, Rueda-Jaimes GE, Latorre JF, Navarro-Mancilla AA, Escobar M, et al. (2009) Validity and reliability of the Center for Epidemiologic Studies-Depression scale in Colombian adolescent students. Biomedica 29: 260–269.
- 28. Gonzalez-Forteza C, Jimenez-Tapia JA, Ramos-Lira L, Wagner FA (2008) Application of the revised version of the Center of Epidemiological Studies Depression Scale in adolescent students from Mexico City. Salud Publica Mex 50: 292–299.
- 29. Soler J, Perez-Sola V, Puigdemont D, Perez-Blanco J, Figueres M, et al. (1997) Validation study of the Center for Epidemiological Studies-Depression of a Spanish population of patients with affective disorders. Actas Luso Esp Neurol Psiquiatr Cienc Afines 25: 243–249.
- 30. Vazquez FL, Blanco V, Lopez M (2007) An adaptation of the Center for Epidemiologic Studies Depression Scale for use in non-psychiatric Spanish populations. Psychiatry Res 149: 247–252.
- 31. Campo A, Diaz LA, Rueda GE (2006) Validity of the brief Zung's scale for screening major depressive episode among the general population from Bucaramanga, Colombia. Biomedica 26: 415–423.
- 32. Aragones Benaiges E, Masdeu Montala RM, Cando Guasch G, Coll Borras G (2001) Diagnostic validity of Zung's self-rating depression scale on primary care patients. Actas Esp Psiquiatr 29: 310–316.
- 33. Martinez KG, Guiot HM, Casas-Dolz I, Gonzalez-Tejera G, Colon de Marti LN (2003) Applicability of the Spanish Translation of the Zung Self-Rating Depression Scale in a general Puerto Rican population. P R Health Sci J 22: 179–185.
- 34. Reuland DS, Cherrington A, Watkins GS, Bradford DW, Blanco RA, et al. (2009) Diagnostic accuracy of Spanish language depression-screening instruments. Ann Fam Med 7: 455–462.
- 35. Ruiz-Grosso P, Osada J, Hoppe W, Pedraz B, Vega-Dienstmaier J (2011) Under reporting of depressive disorders. Rev Peru Med Exp Salud Publica 28: 697.
- 36. Campo-Arias A, Díaz-Martínez LA, Eduardo G, Jaimes R, Cadena LDP, et al. (2006) Validation of Zungs Self-Rating Depression Scale Among the Colombian General Population. Social Behavior and Personality: an international journal 34: 87–94.
- 37. Jegede RO (1979) Psychometric characteristics of Yoruba versions of Zung's self-rating depression scale and self-rating anxiety scale. Afr J Med Med Sci 8: 133–137.
- 38. Fountoulakis K, Iacovides A, Kleanthous S, Samolis S, Kaprinis SG, et al. (2001) Reliability, validity and psychometric properties of the Greek translation of the Center for Epidemiological Studies-Depression (CES-D) Scale. BMC Psychiatry 1: 3.
- 39. Poulin C, Hand D, Boudreau B (2005) Validity of a 12-item version of the CES-D used in the National Longitudinal Study of Children and Youth. Chronic Dis Can 26: 65–72.
- 40. Chabrol H, Montovany A, Chouicha K, Duconge E (2002) Study of the CES-D on a sample of 1,953 adolescent students. Encephale 28: 429–432.
- 41. Hales DP, Dishman RK, Motl RW, Addy CL, Pfeiffer KA, et al. (2006) Factorial validity and invariance of the center for epidemiologic studies depression (CES-D) scale in a sample of black and white adolescent girls. Ethn Dis 16: 1–8.
- 42. Crockett LJ, Randall BA, Shen YL, Russell ST, Driscoll AK (2005) Measurement equivalence of the center for epidemiological studies depression scale for Latino and Anglo adolescents: a national study. J Consult Clin Psychol 73: 47–58.
- 43. Rouch-Leroyer I, Sourgen C, Barberger-Gateau P, Fuhrer R, Dartigues JF (2000) Detection of depressive symptomatology in elderly people: a short version of the CES-D scale. Aging (Milano) 12: 228–233.
- 44. Cole SR, Kawachi I, Maller SJ, Berkman LF (2000) Test of item-response bias in the CES-D scale. experience from the New Haven EPESE study. J Clin Epidemiol 53: 285–289.
- 45. Mahard RE (1988) The CES-D as a measure of depressive mood in the elderly Puerto Rican population. J Gerontol 43: P24–25.
- 46. Tavares S (2007) Validity of the Center for Epidemiological Studies Depression Scale among Brazilian elderly. Rev Saúde Pública 41: 4.
- 47. Nguyen HT, Kitner-Triolo M, Evans MK, Zonderman AB (2004) Factorial invariance of the CES-D in low socioeconomic status African Americans compared with a nationally representative sample. Psychiatry Res 126: 177–187.
- 48. Magruder-Habib K, Zung WW, Feussner JR (1990) Improving physicians' recognition and treatment of depression in general medical care. Results from a randomized clinical trial. Med Care 28: 239–250.
- 49. Romera I, Delgado-Cohen H, Perez T, Caballero L, Gilaberte I (2008) Factor analysis of the Zung self-rating depression scale in a large sample of patients with major depressive disorder in primary care. BMC Psychiatry 8: 4.
- 50. Biggs JT, Wylie LT, Ziegler VE (1978) Validity of the Zung Self-rating Depression Scale. Br J Psychiatry 132: 381–385.
- 51. Chida F, Okayama A, Nishi N, Sakai A (2004) Factor analysis of Zung Scale scores in a Japanese general population. Psychiatry Clin Neurosci 58: 420–426.
- 52. Fountoulakis KN, lacovides A, Samolis S, Kleanthous S, Kaprinis SG, et al. (2001) Reliability, validity and psychometric properties of the Greek translation of the Zung Depression Rating Scale. BMC Psychiatry 1: 6.
- 53. Passik SD, Lundberg JC, Rosenfeld B, Kirsh KL, Donaghy K, et al. (2000) Factor analysis of the Zung Self-Rating Depression Scale in a large ambulatory oncology sample. Psychosomatics 41: 121–127.
- 54. Powell R (2003) Psychometric properties of the Beck Depression Inventory and the Zung Self Rating Depression Scale in adults with mental retardation. Ment Retard 41: 88–95.
- 55. Schrag A, Barone P, Brown RG, Leentjens AF, McDonald WM, et al. (2007) Depression rating scales in Parkinson's disease: critique and recommendations. Mov Disord 22: 1077–1092.
- 56. Kitamura T, Hirano H, Chen Z, Hirata M (2004) Factor structure of the Zung Self-rating Depression Scale in first-year university students in Japan. Psychiatry Res 128: 281–287.
- 57. Range LM, Antonelli KB (1990) A factor analysis of six commonly used instruments associated with suicide using college students. J Pers Assess 55: 804–811.
- 58. McDonald RP (1999) Test theory: A unified treatment. Mahwah, NJ, US: Lawrence Erlbaum Associates Publishers (c) 2012 APA, all rights reserved (Hardcover).
- 59. Revelle W, Zinbarg R (2009) Coefficients Alpha, Beta, Omega, and the glb: Comments on Sijtsma. Psychometrika 74: 145–154.
- 60. Zinbarg RE, Revelle W, Yovel I, Li W (2005) Cronbach's α, Revelle's β, and Mcdonald's: their relations with each other and two alternative conceptualizations of reliability. Psychometrika 70: 123–133.
- 61. Andresen EM, Malmgren JA, Carter WB, Patrick DL (1994) Screening for depression in well older adults: evaluation of a short form of the CES-D (Center for Epidemiologic Studies Depression Scale). Am J Prev Med 10: 77–84.
- 62. Cho MJ, Kim KH (1998) Use of the Center for Epidemiologic Studies Depression (CES-D) Scale in Korea. J Nerv Ment Dis 186: 304–310.
- 63. Dojka E, Gorkiewicz M, Pajak A (2003) Psychometric value of CES-D scale for the assessment of depression in Polish population. Psychiatr Pol 37: 281–292.
- 64. Andriushchenko AV, Drobizhev M, Dobrovol'skii AV (2003) A comparative validation of the scale CES-D, BDI, and HADS(d) in diagnosis of depressive disorders in general practice. Zh Nevrol Psikhiatr Im S S Korsakova 103: 11–18.
- 65. Cheng ST, Chan AC (2005) The Center for Epidemiologic Studies Depression Scale in older Chinese: thresholds for long and short forms. Int J Geriatr Psychiatry 20: 465–470.
- 66. Covic T, Pallant JF, Conaghan PG, Tennant A (2007) A longitudinal evaluation of the Center for Epidemiologic Studies-Depression scale (CES-D) in a rheumatoid arthritis population using Rasch analysis. Health Qual Life Outcomes 5: 41.
- 67. Callahan LF, Kaplan MR, Pincus T (1991) The Beck Depression Inventory, Center for Epidemiological Studies Depression Scale (CES-D), and General Well-Being Schedule depression subscale in rheumatoid arthritis. Criterion contamination of responses. Arthritis Care Res 4: 3–11.
- 68. Taylor R, Lovibond PF, Nicholas MK, Cayley C, Wilson PH (2005) The utility of somatic items in the assessment of depression in patients with chronic pain: a comparison of the Zung Self-Rating Depression Scale and the Depression Anxiety Stress Scales in chronic pain and clinical and community samples. Clin J Pain 21: 91–100.
- 69. Pandya R, Metz L, Patten SB (2005) Predictive value of the CES-D in detecting depression among candidates for disease-modifying multiple sclerosis treatment. Psychosomatics 46: 131–134.
- 70. Fiestas F, Gallo C, Poletti G, Bustamante I, Alarcon RD, et al. (2008) What challenges does mental and neurological health research face in Latin American countries? Rev Bras Psiquiatr 30: 328–336.
- 71. Fiestas F, Gallo C, Poletti G, Bustamante I, Alarcon RD, et al. (2009) Improving mental and neurological health research in Latin America: a qualitative study. BMC Public Health 9: 334.
- 72. Perel P, Miranda JJ, Ortiz Z, Casas JP (2008) Relation between the global burden of disease and randomized clinical trials conducted in Latin America published in the five leading medical journals. PLoS One 3: e1696.
- 73. Miranda JJ, Zaman MJ (2010) Exporting ‘failure’: why research from rich countries may not benefit the developing world. Rev Saude Publica 44: 185–189.