Adolescents in high school suffer from circadian misalignment, undersleeping on weekdays and oversleeping on weekends. Since high schools usually impose early schedules, adolescents suffer from permanent social jetlag and thus are a suitable population to study the effects of social jetlag on both academic and cognitive performance. In this study, 796 adolescents aged 12 to 16 reported information about their sleep habits, morningness-eveningness, cognitive abilities and grade point average.Time in bed on both weekdays and weekends were not related to cognitive abilities, and only time in bed on weekdays was related to academic achievement. Social jetlag was negatively related to academic achievement, cognitive abilities (except for vocabulary and verbal fluency abilities) and general cognitive ability (g), whereas morningnesseveningness was slightly positively related to academic achievement and marginally negatively related to inductive reasoning. Results separated by sex/gender indicated that social jetlag may be more detrimental to girls' performance, as it was negatively related to a greater number of cognitive abilities and grade point average.

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The authors examined how time orientation and morningness-eveningness relate to 2 forms of procrastination: indecision and avoidant forms. Participants were 509 adults (M age = 49.78 years, SD = 6.14) who completed measures of time orientation, morningness-eveningness, decisional procrastination (i.e., indecision), and avoidant procrastination. Results showed that morningness was negatively related to avoidant procrastination but not decisional procrastination. Overall, the results indicated different temporal profiles for indecision and avoidant procrastinations. Avoidant procrastination related to low future time orientation and low morningness, whereas indecision related to both (a) high negative and high positive past orientations and (b) low present-hedonistic and low future time orientations. The authors inferred that distinct forms of procrastination seem different on the basis of dimensions of time.

Individual morningness-eveningness differences explain the rhythmic variations of behavioral and biological patterns. Several studies have corroborated that morningness preference increases over adulthood and aging. Adolescents shift their time of day preferences from morningness to eveningness during puberty. The aims of this study were translate to Spanish the Morningness-Eveningness Scale for Children (MESC) and to analyze age and sex differences. A group of 600 adolescents (aged between 12 and 16 years) participated in the study. Psychometric analysis showed that reliability and factor structure were suitable and similar to previous studies. The results indicated a clear decrease of morningness as of 12 years. Boys were more morningness-oriented than girls in several items of the questionnaire. In view of the results, several educational implications are raised. Keywords: morningness-eveningness, adolescence, age, sexLa tendencia a la matutinidad-vespertinidad permite explicar gran parte de las variaciones rítmicas de patrones biológicos y conductuales. Se ha constatado que con la edad se produce un incremento paulatino de la matutinidad. En población adolescente se ha detectado una mayor tendencia a la vespertinidad. Los objetivos del estudio fueron la traducción y adaptación del Morningness-Eveningness Scale for Children (MESC) a población adolescente, así como el análisis de las diferencias de edad y sexo. En el estudio participaron 600 adolescentes entre 12 y 16 años. Los resultados indicaron que el MESC es un instrumento fiable en población adolescente, siendo su estructura factorial similar a la obtenida en otros estudios. A partir de los 12 años se producía una disminución progresiva de la matutinidad, siendo esta disminución mayor para las mujeres que para los varones en algunos elementos del cuestionario. Se plantean algunas implicaciones educativas a raíz de los resultados obtenidos.