What is to be done about the teenagers? They are squandering sleeping time on electronic gadgets to the point where family life, studies and even health are compromised. And many parents either don’t see the problem or feel powerless to intervene.

Make no mistake -- teens and their sleep, or lack of it, are one of the biggest topics in adolescent health. Study after study repeats that high school kids are not getting enough sleep and this affects their ability to learn, to focus --for example, on an activity like driving -- to keep healthy and fight obesity.

For a while the researchers were hammering the hormone theory: the idea that the physical changes of adolescence change teens’ natural sleep rhythms and make it harder for them to go to bed early -- even though they have to get up early to get to school. (Can’t say that I noticed this during my years at boarding school, ever so long ago.)

The circadian-change diagnosis of teens who fall asleep at their first class of the day is still on the table, along with proposals for starting classes later, but now we are hearing more and more about the sleep-disrupting properties of computers and smartphones, often in combination with more traditional media.

A study published in the journal Pediatrics last year showed that teens kept up their activities late into the night. After 9 p.m., 82 percent of the high school students surveyed were watching TV, 55 percent were using a computer online and 44 percent were talking on the phone — with another 34 percent sending and receiving text messages. Of that group, only 21 percent got the 8 to 10 hours of sleep recommended.

In a study of teens in Belgium in 2007, 40 percent of the 16-year-olds surveyed reported they were awoken at least once a month by a text message, which correlated with higher levels of daytime sleepiness.

Girls are taking their phones to bed, ready to take a call or text at any time during the night.

There are various theories about the precise way these devices affect young people:

Some suggest that the media simply take the place of sleep and exercise. Others point to the arousing content of TV, video games and music as a sleep deterrent. Increased caffeine use could be a factor. And a more controversial hypothesis is that bright lights from the screens trick teenage bodies into delaying the secretion of melatonin, a hormone that helps trigger sleep at night, Wolfson said.  Still others believe it is the use of multiple technological devices at once that keeps teens alert past bedtime.

So, what are parents doing? you ask. Some are onto it.

Stephanie Cassidy, Ryan's 48-year-old mom, said summer rules are more lax, but during the school year she and her husband banned computer use — except for homework — on weeknights. They also enforced a 10 p.m. bedtime and put limits on Xbox and other game use at night...

In West Chicago, Sue Kotche, a mother of three teens, recently began insisting that her kids bring all cell phones downstairs to charge in an office overnight, instead of keeping them at their bedsides. She and her husband already limit their children to one extracurricular activity at a time to keep them from exhaustion.

Looks like parents with backbone are the answer, yet again.

For the record, sleep experts say that adolescents need nine hours sleep -- that’s per night, not starting at 2am or in the middle of maths class.