Cross-cultural validity of the WHO-5 Well-Being Index and Euthymia Scale: A clinimetric analysis

Background: The assessment of psychological well-being and euthymia represents an emerging issue in clinical psychology and psychiatry. Rating scales and indices such as the 5-item version of the World Health Organization Well-Being Index (WHO-5) and the Euthymia Scale (ES) were developed but insufficient attention has been devoted to the evaluation of their cross-cultural validity. This is the first study using Clinimetric Patient-Reported Outcome Measures (CLIPROM) criteria to assess cross-cultural validity and sensitivity of five different versions of the WHO-5 and ES. Methods: A multicenter cross-sectional study involving a total of 3762 adult participants from different European (i.e., Italy, Poland, Denmark) and non-European (i.e., China, Japan) countries was conducted. Item Response Theory models (Mokken and Rasch analyses) were applied. Results: Mokken coefficients of scalability were found to range from 0.42 to 0.84. The majority of the versions of the WHO-5 fitted the Rasch model expectations. Paired t-tests revealed that the Italian and Danish WHO-5 versions were unidimensional. Person Separation Reliability indices showed that the Polish, Danish, and Japanese ES versions could reliably discriminate between subjects with different levels of euthymia. Limitations: A convenience sampling was used, thus limiting the generalizability of study findings. In addition, no measures of negative mental health were administered. Conclusions: WHO-5 can be used in international studies for cross-cultural comparisons since it covers transcultural components of subjective well-being. Findings also suggest that the ES can be used as a cross-cultural screening tool since it entailed the clinimetric property of sensitivity.