Assessing mental well-being in a Sinhala speaking Sri Lankan population: validation of the WHO-5 well-being index.

The WHO-5 well-being index is a widely used, short rating scale that measures subjective well-being. We translated the WHO-5 index into Sinhala and tested its psychometric properties including measurement invariance among diverse groups in a community sample in Sri Lanka. The sample of 267 persons aged between 16 and 75 years was recruited from a semi-urban area. 219 completed a paper-based questionnaire and 48 responded to an online survey. Construct validity was tested for factorial validity (Confirmatory Factor Analysis -CFA), convergent validity and known group validity. Composite reliability for congeneric measures and test-retest reliability were also tested. Multi-group CFA (MG-CFA) was used to test measurement invariance. The translated Sinhala version demonstrated good content and face validity. Internal consistency reliability of the five items had a Cronbach's alpha of 0.85 and test-retest reliability over 2 weeks was satisfactory (Pearson r = 0.72, p < 0.001, ICC = 0.82). Confirmatory factor analysis supported factorial validity with a [Formula: see text] =4.99 (p = 0.28), a RMSEA of 0.03 (90% C.I. =0.00-0.10), a SRMR of 0.02, a TLI of 0.99 and a CFI of 0.99; factor loadings were between 0.55 and 0.89. Measurement invariance was acceptable for configural, metric and scalar invariance for gender. WHO-5 scores were significantly negatively correlated with the Patient Health Questionnaire (PHQ-9) (Pearson's r = - 0.45, p < 0.001) scores and the Kessler Psychological Distress Scale (K10) scores (Pearson's r = - 0.56, p < 0.001). The Sinhala translation of WHO-5 well-being index has shown acceptable psychometric properties and can be used for assessing mental well-being in the community in Sri Lanka. Further testing of the measure with larger and diverse (including different ethnic/cultural) groups are indicated to test measurement invariance of the measure.