Trajectories of insomnia symptoms and insufficient sleep duration in early adolescents: associations with school stress.

Study Objectives: We examined how adolescents' sleep patterns (i.e. insomnia symptoms and sleep duration) change from early- to mid-adolescence and whether adolescents follow different trajectories. Furthermore, we also examined the characteristics of adolescents within different trajectories, with a specific focus on the role of school-related stress.

Methods: We used three longitudinal waves of questionnaire data collected annually from a sample of Swedish adolescents ( = 1294; = 13.2 [range: 12-15 years], = .42; 46.8% girls). Using established measures, the students reported on their sleep duration, insomnia symptoms, and perceived school-stress (including stress of school performance, peer and teacher relations, attendance, and school-leisure conflict). We used latent class growth analysis (LCGA) to identify adolescents' sleep trajectories, and the BCH method to describe the characteristics of the adolescents in each trajectory.

Results: We found four trajectories for adolescents' insomnia symptoms; (1) low insomnia (69%), (2) low-increasing (17%, 'emerging risk-group'), (3) high-decreasing (9%), (4) high-increasing (5%; 'risk-group'). For sleep duration, we found two trajectories; (1) ~8 h sufficient-decreasing (85%), (2) ~7 h insufficient- decreasing (15%; 'risk-group'). Adolescents in risk-trajectories were more likely to be girls and consistently reported higher levels of school stress, particularly regarding school performance and attending school.

Conclusions: School stress was prominent among adolescents suffering from persistent sleep problems, especially insomnia, and deserves further attention.