Assessment, Ahead of Print.
The five-item World Health Organization Well-Being Index (WHO-5) is among the most frequently used brief standard measures to assess hedonic well-being. Numerous studies have investigated different facets of its psychometric properties in adult populations. However, whether these results apply to adolescents is uncertain, and only few psychometric studies employed adolescent populations. Thus, the current study aimed to conduct an in-depth psychometric item response theory analysis of the WHO-5 among adolescents from 43 countries using the Health Behaviour in School-aged Children (HBSC) 2022 data set and investigated its (a) dimensionality and measurement structure, (b) test information values and marginal reliability, (c) cross-country measurement invariance and differential item/test functioning, and (d) convergent validity with other measures related to mental health and well-being across countries. The WHO-5 showed a unidimensional measurement structure and overall high test information values and marginal reliability. Furthermore, although a large proportion of parameters were flagged as non-invariant, differential test functioning of the WHO-5 was only modest. Moreover, the WHO-5 mainly showed a concurring nomological network with the other measures related to mental health and well-being across countries, although with some differences in effect sizes. The WHO-5 Well-Being Index is a psychometrically sound measure that has shown promise for cross-cultural research among adolescents in the included European, Central Asia, and North American countries. The translated versions of the WHO-5 are available at https://osf.io/pbexq/.