More than pre-natal stress, “socioeconomic woes,” or even lack of sleep—of all the factors that lead to behavioral problems in five-year-olds, excessive screen time tops them all.

A new Canadian study reveals that “Kindergarten-aged children who spend more than two hours a day in front of screens are at least five times more likely to be inattentive and seven times more likely to display the symptoms of ADHD than their peers who spend 30 minutes a day or less entranced by tablets” or screens of any sort.

And unlike pre-natal stress or family finances, excessive screen time is easy to fix—as long as we can stand up to the fit-throwing and foot stomping.

Set rules. Even more, find alternatives. Crayons, story Bibles, basketballs, a family hike—all will do more for your child’s mental, physical, and spiritual development than screens.

And maybe hardest of all: set an example—put down that phone.