The UK will ban children under 16 from social media by early next year, replicating a policy that came into effect in Australia in 2025. The move is intended to put children’s well-being ahead of technology companies’ profits. But how will scientists study the effects of the measure and determine whether it is actually having a positive impact?

“We have no evidence either way,” says at Bath Spa University in the UK, who is working with the Australian government to analyse the effects of its own ban and is also advising the UK government. “It’s such new territory.”

Leading the way on research in the UK is the Wellcome Trust, which is already deep into the IRL Trial in Bradford. This has recruited about 4000 kids from 10 schools, aged 12 to 15, who installed an app on their phones to track their social media use. For half of those children, the app also limits access to social apps. The researchers expect to publish their first results in the middle of next year, after the newly announced ban has taken effect. However, at the Wellcome Trust says the findings should still help inform policy.

They will also improve upon existing research that tends to rely on self-reported measures, like asking children or their parents how much time they spend on social media, rather than using more objective metrics. What’s more, the few interventional studies that do exist . “If you’re talking about big changes here around mental health and those sorts of things, you’re not going to see changes in two weeks,” says Etchells.

Australia’s ban came into place in December, which is too recent to gauge its long-term effects. But once national bans like these are in place, it is impossible to do controlled studies, in which two groups of similar people are allocated access or not. What’s more, the results from larger studies on the wider population before and after the ban will be impossible to unpick from other social impacts.

For now, Sebastian is gearing up to run additional studies that hopefully generate at least some results soon after the ban. The UK government expects to bring legislation to Parliament before Christmas, with the policy coming into force in early 2027.

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The Wellcome Trust has invited 14 research teams to submit plans, some or all of which will be funded, into the effects of social media on young people’s well-being. These will take varying approaches to capture as much data as possible, with the goal of eventually synthesising the data into a conclusive result.

Some of these studies will follow existing cohorts and regularly interview them about their mental health and well-being over time, before and after the ban. Sebastian says these approaches can be insightful, but rigid. Other studies are proposing momentary assessments, where participants are sent text messages asking them to complete short surveys on the spur of the moment, capturing a different kind of data. Others may look to analyse data that is already being captured for some insight, such as the rate of hospital admissions or school absences.

With time against them, Sebastian hopes that some results could emerge relatively soon after the ban, but they are likely to be nuanced. For instance, a social media ban could have some positive impacts, but also disruptive ones in the short term, as online supportive networks are lost.

The effects of such bans are also likely to change over the years or decades, as today’s children and younger teenagers approach adulthood having never had access to social media. “It’s not that this is a done deal,” says Sebastian. “Policies could be continuing to change over the longer term, and it’s possible that the findings from our study and others will help to shape those policies iteratively.”

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For now, some are wary that the UK government is taking a reactive stance in the complex problem of poor youth mental health, without the appropriate data. at the University of Oxford told the Science Media Centre that a blanket age ban is a “blunt tool” and a stronger step than current evidence can support, but adds that the Wellcome research is an opportunity to learn whether these measures will “help, harm or neither”.

One thing that could hinder research – and undermine government policy – is the ability of users to skirt the bans. Early reports suggest that facial-recognition technology designed to verify ages online can be , and VPNs make it trivial to appear to websites as a user from another country where age checks aren’t mandated.

Surveys in Australia by the Molly Rose Foundation, a suicide-prevention charity, found that 61 per cent of 12-to-15-year-olds who had accounts on restricted platforms before the ban came into force . The organisation said that given the findings, it would be a “high-stakes gamble” for the UK to follow suit at this stage.

Need a listening ear? UK Samaritans: 116123 (samaritans.org); US Suicide & Crisis Lifeline: 988 (988lifeline.org). Visit bit.ly/SuicideHelplines for services in other countries.

An unprecedented look at how the gut microbiome varies among babies in different parts of the world reveals that infants in the West lack a microbe that is common elsewhere. This could aid the development of probiotics, which are sometimes given to premature babies, that are tailored according to where the infant lives, to maximise the chance of these bacteria becoming established.

The first 1000 days of a child’s life are very important for seeding their microbiome, which influences everything from their immune function and mental health to their future disease risk. Our understanding of this was almost exclusively limited to infants in the West, but now, a global atlas of baby microbiomes is finally providing a broader picture.

at the Wellcome Sanger Institute in South Cambridgeshire, UK, and his colleagues sequenced more than 1900 genomes of a bacterium called Bifidobacteria longum, which has been .

These were taken from stool samples collected across the UK, Sweden, the US, and seven countries in South Asia and sub-Saharan Africa: Bangladesh, Pakistan, Kenya, Malawi, Burkina Faso, Uganda and Zimbabwe.

They zeroed in on two subspecies of B. longum: B. longum longum and B. longum infantis, which have been the focus of most previous infant gut microbiome studies. By combining their data with genomes sequenced in prior studies, the researchers found that around 70 per cent of infants from the African and South Asian countries had B. longum infantis in their guts by 2 months old, compared with fewer than 2 per cent of babies from the UK, US and Sweden. “Infantis is basically missing in Western settings,” says Shao.

In contrast, B. longum longum had established in the guts of about a third of infants from these Western countries by 2 months, compared with fewer than 10 per cent of those across the African and South Asian countries.

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This suggests that B. longum longum and B. longum infantis – which both help to develop the immune system and prevent gut and blood infections – are primarily found in distinct regions, says Shao.

This is probably because they thrive on different diets, he says. “Bifidobacteria help to digest nutrients from breast milk, and the composition of this varies with the mother’s diet, so it could be that longum [longum] is better adapted to a Western diet while infantis thrives on diets in other regions,” he says. The babies without either B. longum longum or B. longum infantis probably had other, similar bacteria established in their gut microbiome, , says Shao.

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This study increased the number of B. longum genomes from South Asia that scientists have ever analysed by about 17 times, and those from Africa by around 11 times. “This is a huge step forward for underrepresented populations,” says at the University of Birmingham, UK.

Probiotics are not generally recommended for full-term babies, but are . Off the back of this study, probiotics could be tailored to the region that the premature infant is from, says Hall. For instance, B. longum infantis probiotics may benefit those in parts of Africa and Asia, but it may not persist as well in the guts of Western infants. “Only by understanding how bacteria differ in various places can we understand which probiotics are going to be the best for kids in particular parts of the world,” she says.