The influence of chronotype on school adjustment, sleep and somatic and mental health among adolescents - nationwide sample across one school year.

Evening-type has been previously associated with sleep problems, and mental and somatic health problems among adolescents. We examined how the self-reported chronotype associates with adolescents' health and school adjustment across a school year. Participants (N = 6522) were 12-16-year-old adolescents across Finland. We used generalized linear models to analyze associations between chronotype and school adjustment, and health variables. Generalized estimating equations (GEE) were further used for longitudinal analysis on how chronotype associated with concentration in lessons and susceptibility to give up on difficult tasks. When comparing with Morning-type, Evening-type was associated more often with difficulties in school adjustment and mental and somatic health issues, such as sleep problems, depressive mood, school burnout symptoms, daytime tiredness, and neck and shoulder pain, lower back pain, and headache influenced by digital media use. Loneliness at school and being less accepted by peers associated with extreme chronotypes, with sense of acceptance among peers showing steepest decline among Morning-types across the school year. Poor concentration in lessons and susceptibility to give up on difficult tasks was highest among Definite Evening-types across the school year although the most dramatic negative shift in susceptibility to give up on difficult tasks were seen among Definite Morning-types. Findings indicate the need for mitigating differences in problems related to managing daily life at school and health between different chronotypes.