LAUSR

ABSTRACT The aim of the present study was to adapt the Morningness-Eveningness-Stability Scale improved (MESSi) to the Spanish adolescent population, testing its factor structure and construct validity. The participants were 725 adolescents (52.9% girls; M = 14.8, SD = 1.99) who completed the MESSi, the Morningness Eveningness Scale of Children (MESC), questions about sleep habits adapted from the School Sleep Habits Survey, and self-reported academic performance. The psychometric results support a three-factor model with the factors of morning affect, eveningness, and distinctness, which show good internal consistency. The pattern of correlations between MESSi and the other measures was in the expected direction. The MESC correlated positively with morning affect and negatively with eveningness, whereas distinctness was uncorrelated. Boys reported higher morningness, whereas girls reported higher distinctness. Eveningness was negatively related to academic performance. Overall, the results support the validity and reliability of the Spanish adolescent version of the MESSi.