Later school start times help teens' moods, study says

The benefits held up months later, according to the study.

Is your teen tired and grumpy? Part of that comes with the territory, but new research shows that it might not be entirely their fault.

A new study published by the Sleep Research Society found support for pushing back school start times, showing that a later start to the day led to more sleep and better mood in teenage girls. The research was conducted at an all-girls school in Singapore and focused on about 150 students in seventh through 10th grade (average age 14). The school delayed its start time by 45 minutes, changing from a 7:30 a.m. to an 8:15 a.m. beginning, and studied the effects on its students.

The benefits held up after nine months, according to the study, an encouraging finding because it implies that changing school start times can have a lasting effect.

Some have worried that delaying school start times could delay bedtimes, thus perpetuating a vicious cycle of inadequate sleep. However, at nine months, researchers found that the participants were spending roughly the same amount of time in bed as they were at the one-month follow-up.

Also at the nine-month follow-up, students had not just an increase in time spent “in bed,” but also an increase in time spent asleep. Participants wore wrist actigraphs, small devices that monitor activity and sleep levels. According to their “actigraphy,” students had roughly 10 more minutes of sleep each night. These increases were not noted at the one-month follow-up, implying that institutional changes like delayed school start times may take some time before they truly affect routines and sleep cycles.

While supported by science, later school times don’t seem to be supported by schools. In 2012, only 17.7 percent of American public schools had a start time of 8:30 a.m. or later -- the average was 8:03 a.m.

By starting school later, critics argue, transportation problems follow, particularly related to school buses during rush-hour traffic. Others worry that delayed school start times will make it hard to schedule after-school activities.

Regardless of your school's start time, pediatricians implore teens to stick to a regular bedtime and limit cellphone, tablet and TV use before bed. According to the National Sleep Foundation, the blue light on screens decreases the body’s natural production of melatonin, wreaking havoc on our sleep cycle. Many argue that a “media curfew” approximately 30 minutes before bedtime would be great for teens.

It couldn’t hurt for parents, either.

Laura Shopp, MD, a third-year pediatrics resident affiliated with Indiana University, works in the ABC News Medical Unit.