A Hartford Healthcare sleep expert says as the summer winds down and school slowly approaches, teenagers should start setting up a sleep routine for themselves.

Dr. Christina Abavana says preschoolers need 11 to 13 hours of sleep a night, while teenagers need eight to 10 hours.

"It's vital for mood. It's vital for physical function. It's vital for learning particularly as kids are going back to school. For memory consolidation and also for anxiety," she says.

She says most Americans are sleep deprived but it's especially important for children to get into a routine even a week or so before school starts to get ready to make that they can sleep well.

Doctors say bright light exposure at night from phones or TV isn't good for sleep.