Why one teenager may need more—or less—sleep than another

Sleep problems contribute to a number of mental health issues in adolescents, researchers say. But a lingering question is whether some teens need more—or less—sleep than others to be healthy and at their best.

A new UCLA study in the Journal of Clinical Child and Adolescent Psychology finds that there are differences among teens in how much sleep they need to maintain the best daily mood. Few teens function well on less than seven hours of sleep a night; more than 11 hours is also not optimal for the vast majority of teens. Most teens need eight to 10 hours of sleep, the researchers found.

"This study contributes to the empirical basis for pediatric sleep recommendations," said the study's lead author, Andrew Fuligni, a professor in residence at UCLA's Semel Institute for Neuroscience and Human Behavior. "Rather than just say 'more sleep is better' and 'everyone should get more sleep,' we also want to know about individual needs for sleep."

To study the relationship between sleep duration and next-day mood, researchers recruited 419 Los Angeles ninth- and 10th-graders. For 14 days, the teens completed three-page-long daily checklists before going to bed and answered questions about the previous night's sleep and the current day's mood. To encourage accurate, daily reporting, the teens folded and sealed each day's checklist, stamping the seal with an electronic time stamper. Teens were offered movie passes for properly completing their checklist tasks.

Researchers found that younger adolescents and those who reported more frequent anxiety or depression symptoms such as crying, worrying and fatigue, experienced their best next-day moods after getting more sleep the night before as compared to older youths and those with fewer symptoms. Researchers said younger adolescents and those who report clinically significant levels of anxiety and-or depression symptoms may need extra hours of sleep to reach peak functioning during the day.

Fuligni said there is a need for follow-up research that studies individual differences in sleep needs for different aspects of health and functioning. His previous work hints that sleep targets for optimal mental health and optimal academic performance may differ.

"As a society, we underestimate how much sleep kids—particularly teenagers—need," Fuligni said. "There's a lot of pressure on them to sleep less, and some youth are sacrificing sleep for things like school and other activities."