The neuroendocrine control of the circadian system: Adolescent chronotype

► Delayed sleep patterns (later chronotype), develop during adolescence in humans. ► Pubertal changes in chronotype occur in many other mammalian species. ► These changes in chronotype differ by sex and are driven by reproductive hormones. ► Fundamental properties of the circadian timekeeping system change during adolescence. ► Despite physiological causes, basic interventions can help adolescent sleep problems.