Well, here’s a turn up for the books. Apparently, and against the better judgement of most parents, spending hours online is good for teenagers.

So if you have a teen who does this, relax, despite the average adolescent screen time having risen from eight hours to 19 hours a week since 1995.

Experts have linked this rapid change to an epidemic of mental health problems such as depression and self-harm.

Some researchers play up the evils of social media saying it’s driving a culture of anxiety. Also, there are worries about teenagers who are playing games instead of exercising or seeing their friends.

But Andrew Przybylski, a psychologist at Oxford University and Netta Weinstein, of Cardiff University, found the opposite. Teenagers who use smartphones, computers and other digital devices for up to four and a half hours a day are happier than those who get less screen time.

Psychologists have called on parents to stop trying to restrict their teens’ use of technology. Data from one in five 15-year-olds in the UK was studied and it was found that they could watch more than three and a half hours of films or television, or use computers for nearly four and half hours a day on weekdays, before they had any negative effects.

These teens were optimistic and resilient. Dr Przybylski said: “Even where screen time gets really excessive, the net negative effect is less than a third of that of a young person getting a good or bad night’s sleep. If you’re going to pick a battle, it might make more sense to focus on getting your kid eating or sleeping well.

“It’s not about turning these devices off but getting involved. My message is – risk making a fool of yourself when you play Minecraft with your children.”

He added that the crisis of mental health problems among adolescents had distracted researchers from the fact that children were overall significantly happier now than in previous decades.

“Kids in the UK are happier, they’re healthier, they smoke less pot, they do fewer illegal substances, and they drink a hell of a lot less than they did 10 years ago,” said Dr Przybylski.

Max Davie, mental health officer at the Royal College of Paediatrics and Child Health, said parents could relax so long as their children’s digital habits were manageable and not spoiling their sleep.

“I’ve never bought the story that screen time is directly toxic,” he said.

“I think there’s reassurance for parents here because a moderate amount of screen time is good. Letting children do things that they enjoy is good, even if they are screen-based things.”