If your teen's lack of sleep is keeping you up nights, here's everything you need to know about what's considered a healthy range.
The National Sleep Foundation recommends teenagers 14-17 years old get eight to ten hours of sleep a night. That range was widened by one hour in 2015, indicating teens may need a little less sleep than originally thought.
"It's really good news to all the parents out there," said NBC News medical contributor Dr. Natalie Azar.
RELATED: Nap time! Researchers say sleeping twice a day is good for you
Still, chronic sleep loss and sleepiness among teens "are a serious threat to the academic success, health, and safety" of young people and an important public health issue, the American Academy of Pediatrics warned in 2014.
Electronics, caffeine and early school start times all contribute to an "epidemic" of insufficient sleep in teenagers, it noted.
"Adolescents are different from adults. As they go through (physiologic) changes, they tend to sleep later," Dr. Danielle Laraque-Arena, former chair of the department of pediatrics at the Maimonides Infants and Children's Hospital of Brooklyn, told TODAY's Matt Lauer.
RELATED: Fall asleep faster and sleep better with this expert advice
The AAP report defined sufficient sleep among teens in high school as at least eight hours of slumber per night.
But that may still be an unrealistic goal for adolescents, who are overloaded with homework, extracurricular activities and part-time jobs, experts say. Or who feel the need to stay up late texting friends or updating Facebook.
RELATED: When 'normal teen' stuff is a warning sign of illness
In fact, if standardized test performance is any indication, 16-year-olds score best with about seven hours of sleep a night, surprising research found in 2012.
Brigham Young University economists Eric Eide and Mark Showalter — who are also dads — used a nationally representative sample of 1,724 students, comparing children’s and teens’ standardized test scores with the amount of sleep they reported.
For older teens, seven hours a night was plenty. The optimal amount of sleep for 12-year-olds was higher, about eight hours, while 10-year-olds did best with about nine hours. The report appeared in the Eastern Economics Journal.
RELATED: School start times are too early and it's harmful to kids, CDC warns
“If your kid’s not getting nine hours of sleep, maybe you don’t have to worry so much,” Showalter said, unless they’re regularly getting significantly less. “Certainly, there is good scientific evidence that extreme sleep deprivation or oversleeping has serious health consequences,” he says.
Showalter believes many recommendations were based on surveys of adolescents in the 1970s. The teens were brought into a lab a few days a year for three years and told to sleep as long as they wanted to. Any parent of a teen knows that how much they want to sleep could be way more than how much they need to sleep.
“We couldn’t find much scientific empirical backing for the common recommendations,” Showalter said, echoing a paper that came out in 2012 in the journal Pediatrics. That report, by Australian researchers, concluded that “no matter how much sleep children are getting, it has always been assumed that they need more.”
What about research suggesting students are more alert in morning classes with later start times?
That might have more to do with how early the teen has to get out of bed, Showalter said, rather than the total time spent in bed.