An hour of screen time immediately before bed is fine for most teenagers, according to research by an Australian university.
But two hours is too much and likely to disrupt their sleep, says Associate Professor Michael Gradisar, a clinical psychologist at Flinders University in Adelaide.
He says a review of four years of studies at the university and around the world shows moderate technology use isn't as harmful for adolescent sleep as many health professionals and parents believe.
"Experiments with video games show that if you give an experienced gamer a violent game before bed, their heart rate is not elevated and they sleep quite fine."
It's like they've adjusted to using technology, he says.