The big picture: In extreme cases, researchers also said that some brain scans of 9- and 10-year-olds who spend more than seven hours a day using electronic devices show a thinning of the brain’s cortex, which usually happens later in development. It’s worth noting these are early results that have not yet been published in a peer-reviewed journal, so they shouldn’t be viewed as definitive. As the NIH’s Dr. Gaya Dowling told “60 Minutes,” “We don’t know if it’s being caused by the screen time. We don’t know yet if it’s a bad thing.”