Children who stare at a screen for more than seven hours a day have different brain structures

Young people who spend more than seven hours a day staring at a screen have different brain structures compared to the average child, according to a landmark US study.

The research, funded by the National Institute of Health and led by the University of California, San Diego, found children who spend more time online have premature thinning of the cortex, the brain's outermost layer that processes sensory information. 

“We don't know yet if it's a bad thing. It won't be until we follow them over time that we will see if there are outcomes that are associated with the differences that we're seeing in this single snapshot,” researcher Dr Gaya Dowling told 60 Minutes. 

Scientists are still not clear whether a thinner cortex shown in brain scans is caused by screen time, or whether children who have the brain structure are more likely to spend time online. They say the findings should be treated with caution.

"Some questions we'll be able to answer in a few years," said Dr Dowling. "But some of the really interesting questions about these long-term outcomes, we're gonna have to wait awhile because they need to happen."

The preliminary results come from the £230 million Adolescent Brain Cognitive Development (ABCD) project, which aims to study the brain development of 11,000 children from the age of nine to early adulthood. 

Scientists, working on 21 sites across the US, are currently interviewing nine and ten-year-olds and scanning their brains as part of the ambitious research project to better understand the impact of technology on health.

The current set of data, taken from 4,500 children, has also revealed that those who spend more than two hours a day looking at a screen have worse memory, language skills and attention span.

The findings are from an observational study- meaning it was not possible to prove that extra time on devices caused the weaker cognitive skills. 

However, experts believe several factors- the impact of blue light on the brain, the online activity itself and the fact time spent on gadgets eats into time which might otherwise be spent exercising, sleeping or taking part in more social or mentally challenging tasks, could explain the links.