The number of tablets, videos, television shows, and smart phone tools marketed toward toddlers and preschoolers has exploded over the last several years, prompting parents to ask, “How safe is screen time for very young children?”

A new study by a clinical researcher at Cincinnati Children’s Hospital (published in JAMA Pediatrics) decided to find a definitive answer. Pediatricians and clinical researchers scanned the brains of children 3 to 5 years old and found that those who watched more than the American Association of Pediatrics (AAP) recommended one hour a day (without parental involvement) had lower levels of brain development in key areas related to the development of language, literacy and cognitive skills.

This is important to note because the brain is developing the most rapidly in the first five years of life. That’s when brains are actively engaged in soaking up knowledge and forming strong connections in language, literacy and cognition. Even before screens became portable and ubiquitous, we have long known that parent-baby face to face or heart to heart engagement form the core of the social engagement system from which the child (and later adult) will function in all future relationships.

Specifically, these new studies show that excessive screen viewing is linked to the inability of children to pay attention and think clearly. There is a definite link between excessive screen time and language delay as well as a decrease in parent-child engagement. This is especially important to consider because today’s portable screens follow kids and parents everywhere – to the dinner table, in the car, during playtime with other kids, even to bed.

More troubling, very young kids are now routinely exposed to screen time. About 90% are using screens by age one, according to one study that used MRIs to research the impact of reading to children versus screen use by kids alone. In this testing, MRI results showed that children who used more than the AAP’s recommended one hour per day of screen time without parental interaction, had more disorganized, underdeveloped white matter throughout the brain.

“We know that early experiences shape brain growth, and media is one of these experiences,” says Leanne O’Neil of INDY Neurofeedback. “Heavy media use does not lead directly to brain damage, but rather, it is too passive for brain development and gets in the way of other experiences that could help children reinforce their rapidly growing brain networks.”

Here are AAP screen time guidelines for young children:

• Babies under 18 months should not be exposed to screen media other than brief video chatting with friends and family. Babies need to interact with caregivers and their environment, so don’t use media as a babysitter.
• By the time a youngster turns two, they can use some interactive touchscreens, as long as parents watch with them and reteach the content.
• Children 3 to 5 years old can benefit from well-designed educational TV shows, which can improve a child’s cognitive abilities, help teach words, and positively impact social development. But just like toddlers, preschoolers learn much better from any educational materials when they are co-viewed with their caregiver, interacting about the material.

“The first years of life need to be focused on human interactions that encourage speaking, interacting socially and playing with loving caregivers,” says O’Neil. “This helps young brains develop thinking, problem-solving and other high functioning cognitive and lifelong learning skills.”