Results of development of the Thai Mental Health Index (the Revised 2025 edition)
DOI:
https://doi.org/10.64838/jmht.2026.288750Keywords:
construct validity, instrument development, item response theory, mental health assessment, psychometric propertiesAbstract
Objective: To develop and evaluate the psychometric properties of the Thai Mental Health Index, including the full and short forms.
Methods: The instrument was developed based on the Thai Mental Health Indicator (2007 edition), followed by content validity and cognitive debriefing. The instrument was then administered to 1,837 Thai people aged 15 years and older from four regions of Thailand and Bangkok. Items were examined for quality and selected using item response theory (IRT). Internal consistency was assessed using Cronbach’s alpha coefficient, while construct validity was examined using second-order confirmatory factor analysis (CFA). Mental health levels and cut-off scores were established using latent class analysis (LCA). Agreement between the different forms was assessed using Cohen’s kappa coefficient.
Results: The Thai Mental Health Index-Revised 2025 version (TMHI-R) was developed in three forms: a 56-item full version (TMHI-R-56) and 20- and 14-item short versions (TMHI-R-20 and TMHI-R-14, respectively). All three forms covered four domains of mental health (mental stage, mental capacity, mental quality, and supporting factor), with Cronbach’s alpha coefficients of .939, .892, and .870, respectively. Second-order CFA demonstrated good model fit with the empirical data for all three forms. LCA supported the classification of mental health into three levels: very good, good, and requiring care. The 20- and 14-item versions showed high and significant agreement with the 56-item version, with Cohen’s kappa coefficients of .836 and .788, respectively.
Conclusion: The TMHI-R, comprising the 56-item full version and the 20-item and 14-item short forms, demonstrated acceptable internal consistency and construct validity, with comparable assessment results across forms. The instruments can be used for research and assessment of the mental health of Thai population aged 15 and older.
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References
Department of Mental Health. Strategic Plan of the Department of Mental Health during the 13th National Economic and Social Development Plan (2023-2027). Nonthaburi: Department of Mental Health; 2022. p. 15-8. (in Thai)
Sangsingkeow P. On mental health. Bangkok: Chuan Printing; 1979. (in Thai)
Department of Mental Health. The words of Professor Phon Sangsingkeow: October 8th, Memorial Day for Professor Phon Sangsingkeow. Nonthaburi: Department of Mental Health; 2015. (in Thai)
Ministry of Public Health. Mental health promotion: the neglected issue. In: Summary of the 6th Global Conference on Health Promotion; 2005 Aug 7-11; United Nations Conference Centre, Bangkok. Nonthaburi: Ministry of Public Health; 2005. (in Thai)
Gray R, Thongthai W, Suwannanoppakao R. Happiness is universal. Nakhon Pathom: Institute for Population and Social Research, Mahidol University; 2010. (in Thai)
World Health Organization. World mental health report: transforming mental health for all. Geneva: World Health Organization; 2022. p. 34-40.
Holmes EA, O'Connor RC, Perry VH, Tracey I, Wessely S, Arseneault L, et al. Multidisciplinary research priorities for the COVID-19 pandemic: a call for action for mental health science. Lancet Psychiatry. 2020;7(6):547-60. DOI: https://doi.org/10.1016/S2215-0366(20)30168-1
Pfefferbaum B, North CS. Mental health and the Covid-19 pandemic. N Engl J Med. 2020;383(6):510-2. DOI: https://doi.org/10.1056/NEJMp2008017
Wongrajit K. Endemic approach to COVID-19. Nonthaburi: Strategy and Planning Division, Office of the Permanent Secretary, Ministry of Public Health; 2022. (in Thai)
Mongkol A, Vongpiromsan Y, Tangseree T, Huttapanom W, Romsai P, Chutha W. Development and testing of Thai Mental Health Indicator (TMHI-55). Bangkok: Agricultural Co-operative Federation of Thailand; 2009. (in Thai)
Kittirattanapaiboon P, Jungsiragulwit D, Tanaree A, Supreeda B. Trend and associated factors of mental health in Thailand: a national survey 2018. Journal of Mental Health of Thailand. 2020;28(2):121-35. (in Thai) DOI: https://doi.org/10.26226/morressier.5d1a036e57558b317a13ff3c
Phruksakannon B, Kittirattanapaiboon P, Tanaree A, Supreeda B. Happiness in Thai population: a 2018 national survey analysis at provincial level. Journal of Mental Health of Thailand. 2022;30(1):75-86. (in Thai)
American Educational Research Association, American Psychological Association, National Council on Measurement in Education. Standards for educational and psychological testing. Washington, DC: American Educational Research Association; 2014. p. 28, 73.
Boateng GO, Neilands TB, Frongillo EA, Melgar-Quiñonez HR, Young SL. Best practices for developing and validating scales for health, social, and behavioral research: a primer. Front Public Health. 2018;6:149. DOI: https://doi.org/10.3389/fpubh.2018.00149
Terwee CB, Prinsen CAC, Chiarotto A, Westerman MJ, Patrick DL, Alonso J, et al. COSMIN methodology for evaluating the content validity of patient-reported outcome measures: a Delphi study. Qual Life Res. 2018;27(5):1159-70. DOI: https://doi.org/10.1007/s11136-018-1829-0
Coste J, Guillemin F, Pouchot J, Fermanian J. Methodological approaches to shortening composite measurement scales. J Clin Epidemiol. 1997;50(3):247-52. DOI: https://doi.org/10.1016/S0895-4356(96)00363-0
Saiyot L, Saiyot A. Educational research techniques. 5th ed. Bangkok: Suweeriyasarn; 2000. (in Thai)
Chomeya R, Tayraukham S, Tongkhambanchong S, Saravitee N. Sample size determination techniques for multivariate behavioral sciences research emphasizing SEM. Journal of Education and Innovation. 2024;26(2):438-47. (in Thai)
Wongwanich S. Educational learning evaluation research. 3rd ed. Bangkok: Chulalongkorn University Press; 2019. (in Thai)
Wichaidit W, Sittisombut M, Assanangkornchai S, Vichitkunakorn P. Self-reported drinking behaviors and observed violation of state-mandated social restriction and alcohol control measures during the COVID-19 pandemic: Findings from nationally-representative surveys in Thailand. Drug Alcohol Depend. 2021;221:108607. DOI: https://doi.org/10.1016/j.drugalcdep.2021.108607
Office of the National Economic and Social Development Council. Population projections for Thailand 2010 - 2040 (Revised edition). Bangkok: Office of the National Economic and Social Development Council; 2019. (in Thai)
Office of the National Economic and Social Development Council, Ministry of Interior. Guidelines for determining the annual budget allocation framework for fiscal years 2025 - 2027: Resolution of the Integrated Provincial Administration Policy Committee (IPAPC) No. 1/2023 on February 27, 2023 [Internet]. Bangkok: Office of the National Economic and Social Development Council; 2023 [cited 2026 Feb 24]. Available from: https://www.nesdc.go.th/. (in Thai)
Bureau of Health Promotion and Environmental Health, Department of Health, Ministry of Public Health. List of Local Administrative Organizations: Information support system for health promotion and environmental health, Department of Health, Ministry of Public Health [Internet]. Nonthaburi: Ministry of Public Health; [cited 2026 Feb 24]. Available from: https://dashboard.anamai.moph.go.th/nehis/cdla (in Thai)
Department of Local Administration. Central information system of Local Administrative Organizations [Internet]. Bangkok: Ministry of Interior; [cited 2026 Feb 24]. Available from: https://info.dla.go.th/eForm/abtData.do (in Thai)
Chutha W, Makkhlai K. Survey results on Thai mental health problems, July 16-23, 2024: A survey on public perception and mental health issues among the Thai population. Nonthaburi: Department of Mental Health; 2024. (in Thai)
Preston CC, Colman AM. Optimal number of response categories in rating scales: reliability, validity, discriminating power, and respondent preferences. Acta Psychol. 2000;104(1):1-15. DOI: https://doi.org/10.1016/S0001-6918(99)00050-5
Nadler JT, Weston R, Voyles EC. Stuck in the middle: the use and interpretation of mid-points in items on questionnaires. J Gen Psychol. 2015;142(2):71-89. DOI: https://doi.org/10.1080/00221309.2014.994590
Mokkink LB, Terwee CB, Patrick DL, Alonso J, Stratford PW, Knol DL, et al. The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: an international Delphi study. Qual Life Res. 2010;19(4):539-49. DOI: https://doi.org/10.1007/s11136-010-9606-8
Samejima F. Estimation of latent ability using a response pattern of graded scores. Psychometrika Monograph Supplement. 1969;34(4 Pt 2):1-100. DOI: https://doi.org/10.1007/BF03372160
Hays RD, Morales LS, Reise SP. Item response theory and health outcomes measurement in the 21st century. Med Care. 2000;38(9 Suppl): II28-42. DOI: https://doi.org/10.1097/00005650-200009002-00007
Cronbach LJ. Coefficient alpha and the internal structure of tests. Psychometrika. 1951;16(3):297-334. DOI: https://doi.org/10.1007/BF02310555
Nunnally JC, Bernstein IH. Psychometric theory. 3rd ed. New York: McGraw-Hill; 1994.
Hair JF, Black WC, Babin BJ, Anderson RE. Multivariate data analysis. 8th ed. Cengage Learning; 2019.
Hu LT, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Modeling. 1999;6(1):1-55. DOI: https://doi.org/10.1080/10705519909540118
Goetz K, Coste J, Ecosse E, McGee H, Braakhuis HE, Rose M, et al. Good practice in the development and reporting of short forms of health status measures. Qual Life Res. 2013;22(9):2603-12.
Collins LM, Lanza ST. Latent class and latent transition analysis: With applications in the social, behavioral, and health sciences. Hoboken (NJ): John Wiley & Sons; 2010. DOI: https://doi.org/10.1002/9780470567333
Cicchetti DV. Guidelines, criteria, and rules of thumb for evaluating normed and standardized assessment instruments in psychology. Psychol Assess. 1994;6(4):284-90. DOI: https://doi.org/10.1037/1040-3590.6.4.284
Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics. 1977;33(1):159-74. DOI: https://doi.org/10.2307/2529310
Topp CW, Østergaard SD, Søndergaard S, Bech P. The WHO-5 Well-Being Index: a systematic review of the literature. Psychother Psychosom. 2015;84(3):167-76. DOI: https://doi.org/10.1159/000376585
Goldberg DP, Gater R, Sartorius N, Ustun TB, Piccinelli M, Gureje O, et al. The validity of two versions of the GHQ in the WHO study of mental illness in general health care. Psychol Med. 1997;27(1):191-7. DOI: https://doi.org/10.1017/S0033291796004242
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