A new magnetic resonance imaging (MRI) cross-sectional study using diffusion tensor imaging (DTI) has found that young children who spend more than an hour a day in front of a screen have more disorganized and underdeveloped white matter than children with lower screen time quotas.

The American Academy of Pediatrics (AAP) recommends an hour of daily screen time, and warns that children who spend more than two hours in front of a screen are at risk for a variety of developmental delays, such as impaired cognition, language delay, poor sleep, and decreased parent-child engagement.

To understand the repercussions of excessive screen time, researchers from the Cincinnati Children’s Hospital Medical Center analyzed screen habits of 47 healthy children between the ages of 3 and 5. The children took a battery of standardized assessments before their MRI, including an expressive vocabulary test and a phonological processing evaluation. The researchers also considered household income, of which the median was $50,001 to $100,000.

They used DTI, an effective tool for mapping white matter, to assess how screen time impacts the brain. DTI measures included parameters such as fractional anisotropy, radial diffusivity, and myelination of white matter tracts. 

The average screen time of the participants was just over two hours a day. The DTI demonstrated that children who exceeded the AAP’s recommended screen time had tracks of white matter associated with underdeveloped executive functions.

“These are tracks that we know are involved with language and literacy. And these were the ones relatively underdeveloped in these kids with more screen time,” said lead study author John Hutton, MD. “So the imaging findings lined up pretty perfectly with the behavioral cognitive testing finding.”