This is the Guardian.

A new academic year is underway and across the country 11 year olds are starting secondary school

and perhaps an even bigger milestone getting their first phones.

For parents this means kids can keep in touch, socialise and stay safe, but phones and

social media apps are also at the centre of worries about bullying, attention spans and plummeting teen mental health.

U.S. teen girls are experiencing record levels of sadness and violence.

There is not sufficient evidence for us to conclude that social media is in fact safe for our kids.

We are seeing mental health concerns at a rate that is extreme and very concerning, so we can call it a crisis.

But what do we really know about the impact of smartphones and social media on the mental health of young people?

And what can we do as parents and as a society

to give kids the best chance of thriving in a digital world?

I'm the Guardian Science Editor Ian's sample and this is Science Weekly.

Dr Amy Orban, you're a research fellow at the University of Cambridge and you lead the Digital

Mental Health Program at the Medical Research Council's Cognition and Brain Sciences Unit.

I'd like to start by defining our terms for the conversation

because we used to talk a lot about screen time. That was the thing we were

worried about traditionally, but if things moved on from there?

Yes, I think screen time is a really unhelpful concept, because while screen time might be useful to think about time maybe not spent exercising or climbing trees or playing the piano.

Actually a lot of the impacts of technology that we care about aren't really dependent

on the amount of time we spend on the screen.

It's what we do with them that really matters and so that's why

there's been a lot of mixed evidence in this space trying to relate screen

...