Psychometric Evaluation of the SWEMWBS in Adolescents in English, Spanish, and French

Brief, cross-lingual and psychometrically robust instruments for adolescent wellbeing are needed to effectively measure, assess and promote wellbeing. We evaluated the Short Warwick–Edinburgh Mental Well-Being Scale (SWEMWBS) in 6,445 adolescents (English n = 5,369; French n = 680; Spanish n = 396). SWEMWBS showed good internal consistency (α/ω ≈ .80), strong convergent validity (Flourishing Scale r ≈ .66; Positive Affect (SPANE-P) r ≈ .70), and a one-factor Confirmatory Factor Analysis (CFA) fit. Multi-group CFA supported configural, metric, and scalar invariance across three languages. However, Graded Response Item Response Theory (IRT) models identified differential item functioning for six of seven items despite scalar invariance, indicating subtle item-level translation effects. SWEMWBS is broadly reliable and unidimensional across these languages, but raw summed scores may be biased. We recommend IRT-based or latent-mean approaches for cross-language comparisons and translation refinement of some items.