The experiment: One week of unlimited screen time for their three kids: Grayson, 10, Wesley, 7, and Lilly, 4. "Five to seven hours a day is common. Less than an hour or two a day is the healthiest" ...

The CDC says kids between the ages of 8 and 10 spend an average of 6 hours a day on screens, and that number jumps to 9 hours a day for teens.

Each extra hour of screen time increased the patient's overall risk by about 0.08 standard deviations in 10-year-olds and by 0.13 standard deviations in 18-year-olds, the study's authors said.

Each extra hour of screen time increased the patient's overall risk by about 0.08 standard deviations in 10-year-olds and by 0.13 standard deviations in 18-year-olds, the study's authors said.

Screen time doesn't just affect mental health . It may also take a toll on physical health, according to new research focused on heart health in children and teens.