Teens with late bedtimes have lower grades

"Going to bed after 11:30 pm, particularly in younger adolescents, predicted worse cumulative grade point average (GPA) at high school graduation and more emotional distress in the college years and beyond," said the study's lead author Lauren D. Asarnow, MA, a doctoral student in the department of psychology at the University of California, Berkeley.

The study gathered data on sleep and the number of hours slept from 2,700 teens age 13 to 18 participating in the National Longitudinal Study of Adolescent Health in two cohorts, one in 1995, the second in 1996. In 2001-2002, as respondents aged, data on academic performance and self-reported emotional health were collected for longitudinal comparison. The overall goal of the study was to examine the relationship between the sleep/circadian patterns of high school adolescents in a nationally representative sample, their overall academic performance in high school and rates of emotional distress reported post graduation.

For both high school cohorts, 23 percent of participants reported going to bed at 11:15 pm or later. By the time these teens reached graduation and college age, late school year bedtimes in high school predicted both lower cumulative GPA at graduation and more emotional distress between age 18 and 26. The researchers noted previous research found that adolescents who prefer late activities and bedtimes (a pattern of behavior often referred to as an evening circadian preference) were tested in the morning; they performed worse on cognitive tasks.

Asarnow urged parents to help youngsters get to bed earlier and added that a teen's sleep behavior is highly modifiable with proper support. However, shifting a teen's bedtime from a late to an earlier hour can be hard, she added, in part because for 30 percent to 40 percent of teens, delayed bedtimes have a biological basis tied to the onset and progress of puberty. Furthermore, academic pressure, habits around technology use and the bedtimes of friends also influence a teen's choice to turn in or stay up late.

Timothy Monk, Ph.D., director of the Human Chronobiology Research Program at the University of Pittsburgh agreed that the need to rise very early for school can put students at risk for underperformance academically and for other problems tied to a lack of sleep. "An early school start time both limits the sleeping time of the student and asks him or her to learn at what is close to the nadir of their circadian cycle."