Has your teen been moodier than usual lately? Surging hormones probably have something to do with it, along with school pressures and normal teen angst. But lack of sleep may also play a bigger part than previously thought, and the whole family may end up paying the price.

A leading sleep expert at Cornell University has compared teenagers to "walking zombies" due to lack of sleep. Recent research has shown that teens with a sleep shortage tend to be far more cranky than usual. They have more trouble concentrating, remembering things and learning, which bodes ill for their time in the chem lab.

And teens aren't just yawning through class. They run a higher risk of driving accidents, injuries and substance abuse, and there's some evidence that too little sleep increases their chances of weight gain, diabetes and migraines. Perhaps most troubling, sleep-deprived teens are more likely to be depressed and consider suicide. 

With the mounting evidence in favor of more sleep for teens, you'd think that letting them snooze would be high on the healthcare agenda. Instead, teenagers today are getting less sleep than ever, according to a large new study published in the Journal Pediatrics.  According to the study, about one third of all 15 year olds say they don’t get at least seven hours of sleep a night — 2 hours less than the 9 hour minimum recommended by the National Sleep Foundation.

How can parents help reverse this trend and help their teens get the sleep their developing brains so badly need?

“We need step back as a nation and a community and look at what we’re doing to kids,” says Jodi Mindell of the Sleep Center of the Children’s Hospital in Philadelphia and a professor of psychology at St. Joseph’s University. Until that happens, parents can help protect their kids sleep without hurting their chances of getting into a good college.

Six ways teens can get more sleep

Establish a lights-out time. Look at what time she needs to be in bed with lights out to get 9 hours of sleep. If you don’t think she will buy into an earlier bedtime, convince her to do a “trial” for one or two weeks — say, lights out at 10:00 p.m. “Often what happens is they feel better, they’re more efficient at doing their homework, and they’ll feel the benefits of getting more sleep,” says Mindell.

You can also skip the trial and simply tell your child that the computer goes off by 10:00 or 11:00, says teen and child therapist Barbara Greenberg, PhD, of Fairfield County, Conn. “I work with many families whose teens are up to 12 or 1:00 a.m. every night,” she says. 

“The reason it works to put limits on computer time — and I’ve done it with my child — is that a lot of kids really want to get all their homework done, but they want to do social media at the same time. This way if they waste their time, they’ll suffer natural consequences, like losing points or not doing well on a test. So the firm limit actually gives them some relief — they can tell their friends, ‘Look, my computer will be off at 11 and I have to get this [homework] done.’”

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Examine extracurricular activities. Parents need to look at their child’s extracurricular activities and cut back if necessary. There’s no hard and fast rule on the number of outside activities a teen should have, but she does need time to decompress, says Greenberg, author of Teenage as a Second Language: A Parents’ Guide to Becoming Bilingual. 

“I tell everyone that kids need at least a half hour or 45 minutes of down time every day so they don’t become little robots,” she says. “They might want to leaf through a magazine, draw, take a quick nap. If they don’t have any time for that and they’re losing the joy in their life, that’s when it’s time to cut back. Kids may find it hard to relax and fall asleep if they don’t have time to unwind.”

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Get electronics out of the bedroom. Staring at computer screens, cell phones, TV or iPads at night delays the release of melatonin, so teens don’t feel tired and may stay up later. Try to get kids off their screens about two hours before bed, if possible. That may mean scheduling computer-based homework earlier in the evening. Keeping electronics out of the bedroom is better so they don’t sneak a peek or have late night text fests with their friends. “Teens get caught up in some pretty meaningless [social media] conversations that can go on indefinitely because they don’t know how to end them,” says Greenberg. “It’s best to keep the source of temptation out of the bedroom.”

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Find out how much caffeine he's drinking. One study found that 73 percent of American children consume some level of caffeine each day. Though soda consumption has gone down, it has been replaced by coffee and caffeinated energy drinks. Make sure they’re not consuming energy drinks, coffee, or even Snapple Iced tea after 1 or 2 p.m.

Wake her up on weekends. On weekends, you need to strike a balance between letting your teens catch up on lost sleep but not letting them sleep so late that it shifts their body clocks. Mindell suggests letting them sleep until 9:00 or 9:30.

Get professional help for persistent insomnia. If your child has trouble falling asleep or staying asleep, be extra vigilant about the sleep hygiene advice. But if the problems persist, you may want to get your child evaluated for depression or anxiety. Says Greenberg: “One of the first symptoms of depression is a change in sleep patterns, so you should absolutely seek help if your child has a problem sleeping.”

Laurie Tarkan is an award-winning health journalist for the New York Times, national consumer magazines and websites.