Sleepy teens haven’t got circadian rhythm

High schools that begin classes as early as 7:30 a.m. deprive teenagers of sleep, and attempts to reset an adolescent’s biological clock fail to solve the problem, a study in the June Pediatrics finds.

Sixty high school students in Evanston, Ill., recorded their sleep times in diaries in August, September, and November of 1997 and in February 1998.