Early School Start Times Linked to Teen Anxiety, Study Finds

Teenagers who wake before dawn to make early school start times may be losing more than sleep — they also face a higher risk of anxiety symptoms, according to new research. High school students in South Korea sleep an average of six hours a night, two hours short of the eight-hour minimum doctors recommend, the National Youth Policy Institute said on the 6th, citing a survey of 8,759 students from fourth grade through the final year of high school. Korean adolescents sleep 7 hours and 18 minutes on average, about an hour less than the 8-hour-22-minute average among teenagers in OECD member countries.

Research now suggests that early school start times do more than cut sleep short — they also affect adolescent mental health. A paper by researchers at the University of Southampton in Britain, published in the journal Sleep Medicine Reviews, found that "social jet lag" among adolescents is associated with anxiety symptoms. Social jet lag refers to the shift in sleep timing between weekdays and weekends — the gap between waking earlier than the body clock dictates in order to meet school schedules, and sleeping in on weekends to make up the shortfall. During adolescence, the body clock naturally shifts later as puberty progresses. The onset of melatonin secretion, the sleep hormone, is pushed back, delaying both bedtime and wake-up time. The problem is that this change in circadian rhythm collides head-on with early school start times, creating a daily mismatch between the body clock and the social schedule.

The researchers reviewed 2,138 related studies and selected 18 for final analysis, conducting a meta-analysis of data on 235,526 participants across 12 of them. They found that the larger the social jet lag, the more severe the anxiety symptoms. The effect size was small, but the direction was consistent. The researchers stressed that delayed body clocks in adolescents should not be treated as a matter of personal habits alone, but examined alongside social factors such as school start times. They also recommended behavioral strategies to help teenagers maintain regular and sufficient sleep as a way to support their mental health.