When was the last time you told your teen to just go to sleep? Better yet, what is the bedtime mandate you’ve given to your teenager? I can hear the chuckles already. I know. Communicating with your moody kid is difficult enough behind closed doors, under headphones and while competing with the glare of a screen. But rest is crucial for the teenage brain, and parents need to talk about sleep and enforce bedtime rules.

When I was a teen, going to sleep really wasn’t a problem. My bedroom was just where I slept, did homework and only sometimes talked on the telephone. Most of my life we had two main phones, one in the kitchen and the other in my parents’ bedroom. Telephone conversations were usually whispered by me or spoken in code. The point being that they were usually public and hence short. Now kids huddle under the covers texting, typing and corresponding all night. As parents, we have very little control over the digital communication that is keeping our teens awake—or do we?

As we ease into back-to-school mode, monitoring and enforcing lights-out takes on an incredible amount of importance. Sleep shortages or insufficient sleep in teens (which is less than 8 to 9 hours per night) account for mood changes like depression, increased fatigue, cognitive deficits, inattention, poor grades, substance use and car crashes.

As parents, we have the opportunity to discuss and plan a bedtime with our teens, take away their cell phones and educate them about the importance of getting enough rest. A sleep-deprived teen can be an unhappy and potentially unhealthy child. Will you take the time to decide right now that you’ll start the school year off right? Post a comment and let me know you’re committed. Need ideas for getting your teen to hit the sack? Try these smart solutions.

Janet Taylor, M.D., M.P.H., is a mother of four, a psychiatrist in New York City and director of guest support for The Jeremy Kyle Show. Follow her on Twitter @drjanet.

Got a question for Dr. Janet? Email her at askdrjanet@familycircle.com.