The difference in sleep, depression, anxiety, and Internet addiction between Korean adolescents with different circadian preference

Objectives: Compared to adults, adolescents tend to prefer evening times developmentally. The orientation toward evening times is associated with behavioral and emotional problems. Thus, this study examined the association of circadian preference with sleep-related variables, depression, anxiety, and Internet addiction in Korean adolescents. Materials and Methods: Participants completed the questionnaires measuring sleep pattern, sleep problem, depression, anxiety, and Internet addiction. Results: Among 765 students (age range: 13-17 years), 211 students (N-male = 134) were allocated into morning types (MT) and 258 adolescents (N-male = 147) were allocated into evening types (ET) based on scores of the Morningness-Eveningness Scale. Adolescents without circadian preference (N = 296) were defined as neither type (NT). ET, compared to MT and NT, woke up later in the weekend, showed delays in bedtimes, and spent shorter time sleeping. They also reported a higher level of daytime sleepiness, insomnia, and depression than NT. However, the group difference in wake time on school days was not significant, and adolescents showed mild insomnia regardless of their circadian preference. Although smartphone using time in the weekend was significantly different between groups, group difference in Internet addiction was significant only when gender was adjusted. Conclusion: Circadian preference was associated with sleep patterns and sleep problems in Korean adolescents. ET showed significantly different sleep patterns compared to MT and NT. ET not only reported a higher level of daytime sleepiness and insomnia but also more depressive symptoms compared to NT. These findings suggest that the uniqueness of adolescence and environmental factors seemed to influence the association of circadian preference with mental problem.