The teenage body clock adjusts to social schedules more than natural daylight

Adolescents (n = 112) showed earlier sleep patterns during school weeks compared to holidays, indicating social demands influence circadian timing.

• Circadian rhythms of adolescents' sleep were closely aligned with their behavioral light-dark cycles influenced by social time.
• Melatonin onset (DLMO) tracked the shorter sleep duration observed during school weeks.
• The timing of sleep was consistent between school and holiday periods, despite differences in sleep duration.
• Adolescents went to sleep later and woke up earlier on school nights, potentially affecting their alertness levels.
• Social constraints and light exposure from both natural and artificial sources may significantly impact circadian clock regulation.

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