Psychometric properties and longitudinal measurement invariance of the Brazilian version of the subjective happiness scale in adolescents

Background Happiness is a subjective construct. Validation studies to confirm validity and reliability of happiness measures are needed to verify its applicability in research and clinical fields. Aim The aim of this study was to test the psychometric properties and longitudinal measurement invariance (MI) of the subjective happiness scale (SHS) in adolescents. Methods A longitudinal study was conducted with a random sample of 1134 12-year-old adolescents from Santa Maria, a southern city in Brazil, starting in 2012. Two years later, 746 adolescents were reassessed, with an average age of 14. The Brazilian version of the SHS, which is composed of 4 items, was administered by a face-to-face interview. Reliability (Cronbach's alpha), reproducibility (intraclass correlation coefficient - ICC), discriminant validity, confirmatory factor analysis (CFA), convergent validity, and MI were performed through the multigroup CFA. Socioeconomic, clinical, and subjective variables were also collected through clinical examinations and structured questionnaires by calibrated and trained dentists. Results Cronbach's alpha and ICC results were moderate (0.51 and 0.70, respectively). The scale was able to discriminate subjective happiness between different oral health groups and socioeconomic status. The CFA revealed a good fit model in both collections, confirming the validity of the scale. Convergent validity was satisfactory, demonstrating that the SHS is similar in theoretical concepts with a subjective scale. Moreover, MI showed a goodness-of-fit statistics across time points. Conclusion The Brazilian version of SHS showed adequate validation properties and longitudinal measurement among adolescents. Relevance for patients These findings are important for studies that evaluate happiness and oral disorders, through cross-section and longitudinal studies.