Nearly every 12-year-old now owns a smartphone - but how is it affecting their brains?

With nearly every 12-year-old in the country now owning a smartphone, more and more experts are asking how they could be affecting children's brains, ITV News Presenter Faye Barker reports

Children's use of smartphones is a topic that's buzzing from parents at the school gates to the corridors of Westminster.

With 91 per cent of 12 to 15-year-olds now owning a smartphone, teachers, scientists, politicians and health professionals are all asking if they're safe for children.

One of the biggest concerns is unrestricted access to the internet and social media, with a growing body of research finding that it's negatively impacting children's mental health, sleep and learning.

This week the Safer Phones Bill was introduced in Parliament by Labour MP Josh MacAlister, calling for a law to build on current guidance that bans smartphones in schools.

Other provisions include strengthening the regulator Ofcom's powers to protect children from apps that are designed to be addictive, and raising the age from 13 to 16 when companies can acquire data from children, without their parents consent.

Kate Edwards from the NSPCC says the current "internet age" of 13 doesn't keep children safe.

"The age limit for most social media accounts is 13, and this is actually rooted in data laws rather than any considerations around safety," she says.

"Many safety considerations have just been built on that age, rather than actually taking into account the age and stage development of children, and when might be appropriate for them to engage with these services."

Teenagers in the UK can spend up to nine hours a day on a screen, and research for the Education Select Committee has found that a quarter of children and young people use smartphones in a way that's consistent with behavioural addiction.

For ITV's Tonight programme, I went to the University of Reading to meet Neuroscientist Professor Ciara McCabe who has been researching the brain's reward system:

She says: "When you're an adult and you're looking at a smartphone, you have your brain's reward system activated, but you also have your prefrontal cortex fully developed, and that's like a control system.

"There's evidence to suggest that adolescent brains or teenage brains respond differently, and in particular to rewarding experiences. Younger people might be a little bit more susceptible to social media because they don't have a fully developed control centre in their brain yet."

Schools have found themselves at the centre of the debate, with government guidance saying smartphones should be banned in schools. In reality, that means it's left to head teachers to decide what to.

Damian McBeath, headteacher at The John Wallis Academy in Ashford, Kent, told me what he's been up against:

"Students were gathering in toilets and taking photos and videos of people's faces and then they were posted all over social media groups. There were occasions where phones were being used in lessons and teachers were being filmed and then that was being uploaded."

These problems have led to a big change. Since the start of this year, pupils at the school place their phones in a pouch with a magnetic lock, which makes them inaccessible for the rest of the school day. Mr McBeath says the result has been transformational:

"When we first announced it, I think there was a feeling of disbelief. There was an initial cost of about £35,000, but since we implemented it in January, we have seen a significant reduction in the number of detentions that teachers have given out.

"So that's reduced by 40%. We're seeing less truancy in school, and reports of online bullying, reports of incidents or online abuse are at a five year low. I think staff too are happier in a school where they know they're protected and safeguarded."

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But what did the pupils think? I sat down with a group aged between 11 and 15, and although they found it hard without their smartphones at first, they all spoke of benefits.

Alicia said: "Many more people are learning and they're not getting distracted by all the notifications they're receiving".

Daniel told me that things that might have turned into arguments are now being resolved in person rather than being magnified online.

Blake, who only started secondary school this September, admitted that when he has his smartphone outside of school, he finds it hard to not keep looking at his social media feeds, even when he sees content that makes him feel sad.

Some tech companies are now developing phones that are less smart, but still have certain features like GPS tracking that many parents find reassuring.

Next year tougher Ofcom rules should better protect young people as part of the Online Safety Act. In the meantime, more parents are asking if children should even have a smartphone at all.

You can find out more in an episode of the Tonight series; Smartphones: Time To Live Without Them? Thursday 17 October at 8:30pm, ITV1 and ITVX

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