The Impact of School Start Times on Adolescent Health and Academic Performance, In the early 1990s, researchers from Brown University (1) and the University of São Paulo (1.5) found initial evidence that circadian biology drives the delayed sleep-wake patterns of adolescents. (1, 1.5) Subsequent studies have confirmed puberty’s onset marks the beginning of a phase shift, with adolescents going to bed later and rising later than younger children. (2, 2.5, 3, 4) Typically….