Extending the CASO-N24 to Late Adolescence: Psychometric Properties and Measurement Equivalence in a Peruvian School Sample

Background: Social anxiety in adolescence is a prevalent mental health concern characterized by intense fear of negative evaluation in social situations. The Social Anxiety Questionnaire for Adolescents (CASO-N24) is a Spanish-language instrument requiring validation in Peruvian populations. Objective: This study aimed to validate the CASO-N24 in Peruvian adolescents aged 12–17 years, extending its application beyond the original 9–15-year range, and examine its psychometric properties including factorial structure, measurement invariance, convergent validity, and internal consistency. Methods: A stratified probability sample of 710 adolescents (352 males, 358 females; M=14.82 years, SD=1.45) from four northern Peruvian educational centers completed the CASO-N24 and ASQ-14. Exploratory and confirmatory factor analyses, multigroup invariance testing by age and gender, convergent validity assessment, and reliability estimation (Cronbach’s α and McDonald’s ω) were conducted using polychoric correlations and robust estimation methods. Results: The six-factor structure was replicated, explaining 47.13% of variance with factor loadings ranging .48–.78. Model fit indices were excellent (GFI=.981, AGFI=.976, NFI=.971, SRMR=.046). Complete measurement invariance was achieved across age groups (12–15 vs. 16–17 years). Partial invariance by gender was observed, with differential item functioning identified in item 17. Convergent validity was confirmed through moderate-to-high correlations with ASQ-14 (males: r=.622; females: r=.604). Internal consistency was adequate (total scale ω=.95; subscales ω=.69–.82). Conclusion: The CASO-N24 demonstrated robust psychometric properties for assessing social anxiety in Peruvian adolescents aged 12–17 years, supporting its multidimensional structure and utility for early detection in school settings while highlighting gender-specific response patterns warranting clinical consideration.