Validation of the WHO-5 as a screening tool for depression among young adults in Malaysia

As depression has become a major disease burden in Malaysia, an easy-to-use tool with good psychometric qualities is urgently needed to facilitate the screening process. The current study aimed to investigate the psychometric qualities of the 5-item World Health Organization Well-being Index (WHO-5) and the optimal cut-off point for depression screening in the Malaysian context. A total of 610 undergraduate students answered an online survey consisting of the English version of the WHO-5 and Patient Health Questionnaire-9 (PHQ-9). Results of confirmatory factor analysis supported the single-factor model. The present study found the WHO-5 had a good reliability and concurrent validity. Moreover, receiver operating characteristic analysis indicated that ≤13 was the optimal threshold with acceptable sensitivity and specificity to detect depression. This study concludes the WHO-5 is a brief, valid, and reliable depression screening tool among young adults in Malaysia.

Depression has become a significant public health problem globally (Herrman et al., 2019). In Malaysia, depression has affected 2.3% of the adult population and has become the major cause of disease burden (Institute for Public Health, 2020). Often, depression is a result of complex interaction of biological, psychological and social factors (Serafini et al., 2016;Serafini et al., 2017). Therefore, a psychometrically sound screening tool is urgently needed for depression research and intervention. While a number of depression screening instruments (Rusli et al., 2017;Sherina et al., 2012) are available, most of them acquired negative phrased items that ask explicitly for depressive symptoms. Those items may be underreported due to the shame and self-stigma associated with psychic disorder when admitting dysfunction in oneself (Sisask et al., 2008), particularly in Asian culture (Yang et al., 2020). The World Health Organization Well-being Index (WHO-5;World Health Organization, 1988) is a positivelyphrased measure of subjective well-being and has also been widely used for depression screening (Topp et al., 2015).
Although the WHO-5 has been validated in different countries, the psychometric properties and cut-off point of the scale have not been established in Malaysia. This study aimed to investigate the factorial structure, validity, reliability, and the optimal cut-off point of the WHO-5 as a brief depression screening tool in Malaysia. The results are expected to recommend the cut-off point for depression screening among young adults in Malaysia and verify the usability of the WHO-5 in cross-cultural studies.

Design, Participants, and Procedures
Cross-sectional design and convenience sampling were employed to recruit 615 undergraduate students. The inclusion criteria for participants in this study were (a) undergraduate students aged between 18 to 35 years old; (b) Englishliterate; (c) have access to the internet. Five participants who answered less than 50% of the items were excluded. Among the 610 respondents (M age = 21.806, SD = 2.112; range = 18 to 35), 76.9% were female. The majority of them (84.9%) were Chinese, followed by Malays (7.4%), Indians (6.6%), and other ethnicities (1.2%). Respondents were students from different years of study, including Year 1 (19.0%), Year 2 (33.6%), Year 3 (34.9%), Year 4 and above (12.3%), and one as unidentified. Data were collected through social media (e.g., Facebook) from January to March 2021. Ethical approval was obtained from the university (ref. no: [masked for review]). Data was analysed using JASP 0.14.1.0.

Measurements
As English is the medium of instruction in most of the universities in Malaysia, the study employed the original English version of the following scales.
World Health Organization Well-Being Index (WHO-5;World Health Organization, 1998) The WHO-5 is a brief, self-reported scale with five items that are positively worded that measures people's current level of subjective well-being in the past two weeks. Items are rated on a 6-point Likert scale (0: At no time; 5: All of the time). The raw score ranges from 0 to 25, which higher scores indicate better mental well-being. Generally, scores below 13 may indicate poor well-being. The WHO-5 has portrayed good psychometric properties (i.e. validity and internal consistency) across numerous validation studies (e.g. Cichoń et al., 2020). Past studies have suggested satisfactory results when the WHO-5 was used for depression screening (e.g. Guðmundsdóttir et al., 2014). In a systematic review, the sensitivity and specificity of the WHO-5 as depression screening tool were .86 and .81 respectively (Topp et al., 2015).
Patient Health Questionnaire-9 (PHQ-9; Kroenke et al., 2001) PHQ-9 is a 9-item measure for the severity of depressive symptoms in the past two weeks. Items in the PHQ-9 represent the nine criteria stated in Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) for diagnosing major depressive disorder. Items are rated on a 4point Likert scale (0: not at all; 3: nearly every day). The overall sensitivity and specificity of the PHQ-9 ranged from 0.37 to 0.98 and 0.42 to 0.99 respectively in a systematic review (Costantini et al., 2021). PHQ-9 showed a sensitivity of .87 and specificity of .82 in the Malaysian context (Sherina et al., 2012). Total score of the PHQ-9 ranges from 0 to 27. In this study, PHQ-9 yielded a good internal consistency (Cronbach's alpha [⍺] = .869) and a score of ≥10 indicated a current depressive episode.
Reliability was examined using ⍺ coefficient, while the concurrent validity of the WHO-5 was examined by correlating with the scores of PHQ-9 using Pearson's correlation. Moreover, receiver operating characteristic (ROC) analysis was conducted against PHQ-9 scores to examine the optimal cut-off point for the WHO-5. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to examine the diagnostic accuracy for the WHO-5.

Reliability and Validity
The WHO-5 showed good internal consistency (⍺ = .896), implying that the items are conceptually relevant with each other. Moreover, the WHO-5 score had a negative correlation with the PHQ-9 score, r(608) = −.558, p < .001. The results support the concurrent validity of the WHO-5, indicating that the WHO-5 has moderate agreement with the PHQ-9, a goldstandard of depression screening .

The Optimal Cut-off for the WHO-5
Under the cutoff of 12.5 / <13, the area under the ROC curve was .780, sensitivity = .779 and specificity = .672. The PPV and NPV of the WHO-5 was .670 and .753, respectively.

Discussion
Our study found good reliability and validity of the WHO-5 among young adults in Malaysia, with an optimal cut-off point of <13 for depression screening. Our results provide empirical evidence of the applicability of the WHO-5 in Malaysia context. Consistent with past findings from young adults (Ghazisaeedi et al., 2021) and people with medical conditions (Cichoń et al., 2020;Dadfar et al., 2018;Eser et al., 2019), the CFA results support the single-factor model. Adding error covariance between items 1 (assessing general mood; "I have felt cheerful in good spirits") and 4 (assessing sleep quality; "I woke up feeling fresh and rested") improved the model fit. This could be due to a general mood associated with sleep quality in our sample.
The WHO-5 also showed good reliability and concurrent validity among young adults in Malaysia. Our finding is similar to those studies conducted with clinical and community samples (e.g., Halliday et al., 2017;Omani-Samani et al., 2019;Perera et al., 2020).
The present study is the first to suggest the cut-off value of the WHO-5 in the Malaysian context. Consistent with past studies (e.g., Christensen et al., 2015;Ghazisaeedi et al., 2021;Halliday et al., 2017), the WHO-5 shows acceptable sensitivity (78%) and specificity (67%) for the optimal (12.5 / ≤13) cut-off value. The findings highlight the usefulness of the WHO-5 across cultural contexts.
It is noteworthy that the relatively low specificity may lead to false-positive cases. Nevertheless, it is acceptable because people who reported low levels of well-being may suffer from other forms of mental disorders (e.g., anxiety disorders, adjustment disorder) and a follow-up visit to mental health professionals is typically harmless. Importantly, the NPV (0.75) is good, indicating the WHO-5 yielded few false-negative results that may result in unattended mental health problems.
Despite the encouraging results found in the present study, it is important to note that a few limitations were presented in this study. First of all, the sample was limited to university students, who have good to excellent English proficiency. Therefore, the findings may not be fully generalizable to the general population in Malaysia. Since Malaysia is a multi-ethnic and multilingual country, it is recommended to translate the scale into local languages (e.g., Malay, Mandarin, and Tamil languages).

Conclusion
This study adds to the growing options of depression screening tools in Malaysia. The positively worded WHO-5 is a rapid, non-intrusive mental health screening instrument that can be used by both mental health professionals as well as non-specialized staff to identify depression among young adults in Malaysia. The freely available, and easy selfadministered questionnaire may be also suitable to be used in large-scale epidemiological studies.
Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors. The draft of the manuscript was written by Kah-Yue Low and Kai-Shuen Pheh, and Chee-Seng Tan commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding The authors did not receive support from any organization for the submitted work.
Data Availability The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations
Ethical Approval All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). This study has been approved by the UTAR Scientific and Ethical Review Committee, with reference number: U/SERC/176/ 2020.

Consent to Participate
Informed consent was obtained from all individual participants included in the study.

Conflict of Interest
The authors have no conflicts of interest to declare that are relevant to the content of this article.