“If you look at that screen too long, you’ll get square eyes” is a phrase many kids are tired of hearing, but while this is just a trick parents use to peel their children away from the TV, new research suggests that too much screen time really can impact a child’s body.

A huge $300-million study by the National Institutes of Health (NIH) is looking into how being constantly surrounded by screens might affect children’s health. At 21 sites across the US, researchers are interviewing 11,000 children aged 9-10, as well as scanning their brains. They will follow this cohort for over a decade.  

The research has already begun, and the NIH’s Dr Gaya Dowling recently shared some of its early findings with CBS’ 60 Minutes. The first set of data comes from studying a total of 4,500 children, and the results are a little concerning.

Using MRI scans, the scientists found that children who spend over seven hours a day glued to laptops, tablets, game consoles, and TVs have noticeable changes to the structure of their brains in the form of premature thinning of the cortex. “That’s the wrinkly outermost layer of the brain that processes information from the five senses,” explained Dr Dowling.

“We don't know if it's being caused by the screen time,” she added. “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.”

While we’ll have to wait to see exactly how this impacts the children – or if it does at all – the researchers also found a worrying side effect of screens in children who use them for more than two hours a day. These kids did worse at thinking and language tests, suggesting that too much screen time has a negative impact on cognition.

As the study aims to look at the effects of screen time over a significant period of time, more details about the impacts and how they might affect a person’s life later on remain to be seen.

We already know that our obsession with screens could be damaging our health, but we still need more research to determine the exact extent. A study from August found that the blue light emitted by screens can literally kill the cells in our retinas. Other studies have shown that the bright light of screens means that children and adolescents get less sleep and that the quality of this sleep is poorer.

The American Academy of Paediatrics currently suggests that children younger than 18 months should be kept away from screens apart from video-chatting, while those aged 2-5 should use high-quality screens for no more than an hour a day. Screen time should be limited for those over the age of six, and it should not be allowed to get in the way of sleep or exercise.