Young children who get more screen time than doctors recommend have differences in parts of the brain that support language and self-regulation, a study at Cincinnati Children’s Hospital Medical Center has found.

It's not clear how the changes affect a child's development, the researchers said.

The study put 47 healthy Cincinnati-area children between 3 and 5 through magnetic resonance imaging of their brains as well as cognitive testing. While the study did not learn how screen time changed the brains, it did show that skills such as brain processing speed were affected.

"Screen-based media use is prevalent and increasing in homes, childcare and school settings at ever younger ages," said Dr. John Hutton, the author of the study and director of the Reading & Literacy Discovery Center at Cincinnati Children’s Hospital.

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"These findings highlight the need to understand effects of screen time on the brain, particularly during stages of dynamic brain development in early childhood, so that providers, policymakers and parents can set healthy limits," he said.

The Cincinnati Children’s study was published in the journal JAMA Pediatrics and follows a string of studies released this year on the effects of screen time on the youngest humans.

A Canadian study published in April found that screen time can affect attention spans in preschoolers. A March study found that mobile phone use can delay expressive language in 18-month-olds. Another JAMA Pediatrics study in April found that screen time can affect how a child performs on developmental testing.

A study at Cincinnati Children's Hospital Medical Center shows that young children who use screen media more than the recommended amounts have changes in the white matter of the brain, which affects language and self-regulation. This brain image shows white matter tracts with lower structural integrity associated with more screen time in these children. Affected areas are in blue. (Photo: Provided)

The Cincinnati Children’s study assessed screen time using the recommendations of the American Academy of Pediatrics. The academy suggests, for example, that children younger than 18 months should avoid all screen media other than video chatting. Parents should monitor digital media and watch it with their children.

For children between 2 to 5, the AAP recommends limiting screen time to an hour a day. Parents should designate media-free times, such as dinner or driving, as well as media-free locations at home, such as bedrooms.

The children in the Cincinnati study completed standard cognitive tests and a special test called diffusion tensor MRI, which estimates white matter integrity in the brain.

Researchers gave the parents in the study a 15-item screening tool based on the AAP's media recommendations. Those scores were matched to the cognitive test scores and the MRI measures, controlling for age, gender and household income.

Higher scores on the screening tool were significantly associated with lower expressive language, the ability to rapidly name objects or processing speed and early reading skills, the study found.

In addition, higher scores also were associated with lower brain white matter integrity, which affects organization, and myelination – the process of forming a myelin sheath around a nerve to allow impulses to move more quickly, in tracts involving language executive function and other literacy skills.

Hutton said, "While we can’t yet determine whether screen time causes these structural changes or implies long-term neurodevelopmental risks, these findings warrant further study to understand what they mean and how to set appropriate limits on technology use."

Hutton said his team has several follow-up papers in the works including a study showing the beneficial links between home reading practices and brain development in preschool-age children. The work builds on five other studies Hutton’s team has published since 2015 to link home reading to brain development before kindergarten.

Hutton said he wants to do a bigger study starting in infancy, but that will depend on getting the funding for the research.

The Cincinnati Children's Research Foundation funded the study with a Procter Scholar Award.