(BLOOMBERG) — Smartphones, tablets and video games are physically changing the brains of adolescents, early results from an ongoing $300 million study funded by the National Institute of Health have shown, according to a report by “60 Minutes.”

Scientists will follow more than 11,000 nine- to 10-year-olds for a decade to see how childhood experiences impact the brain and affect emotional development and mental health. The first bits of data suggest that the onslaught of tech screens has been transformative for young people — and maybe not for the better.

In brain scans of 4,500 children, daily screen usage of more than seven hours showed premature thinning of the brain cortex, the outermost layer that processes information from the physical world. Though the difference was significant from participants who spent less screen time, NIH study director Gaya Dowling cautioned against drawing a conclusion.

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