Manjón Caballero, José LuisDíaz Morales, Juan Francisco2025-06-062025-06-062025Manjón-Caballero, J.L. & Díaz-Morales, J.F. (2025). Morningness–Eveningness Questionnaire: Reliability and factorial structure of the full and reduced versions in Spanish adolescents, Chronobiology International, DOI: 10.1080/07420528.2025.25096340742-052810.1080/07420528.2025.2509634https://hdl.handle.net/20.500.14352/121016This study analyzed the suitability of the Morningness–Eveningness Questionnaire (MEQ) for Spanish adolescents, focusing on reliability, structure, and age/sex invariance. 2,268 adolescents (49.1% girls, aged 12–17) participated. Four MEQ items were unsuitable, leading to a 15-item version (MEQ-15) with good reliability and fit to a bifactor model: general morningness–eveningness factor and awakening time, sleep time, and time of greatest efficiency factors. The reduced MEQ (rMEQ) also fit a one-factor model. Sex and age invariance were tenable for the general factor of MEQ-15 and rMEQ. Morningness declines during adolescence, with boys showing more morningness than girls. Both versions show good psychometric properties.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal article1525-6073https://doi.org/10.1080/07420528.2025.250963440433950https://www.tandfonline.com/doi/full/10.1080/07420528.2025.2509634open access612.821Morningness‒Eveningness QuestionnaireReduced MEQAdolescentsFactorial structureSex and age factorial invariancePsicología (Psicología)61 Psicología