Too Much Screen Time Harms Brain Development

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Watching more than two hours of screens a day may harm the structural integrity of white matter in preschoolers' brains, with implications for language and literacy skills. Children under 2 years shouldn't use screens, but even those 2 and over may face lifelong consequences of too much screen time during childhood

You may want to think twice before gifting your child a new tablet or cellphone this holiday season, as increasing research suggests screen time may cause more harm than good. 

Preschool-aged children may be particularly at risk, which is why the American Academy of Pediatrics recommends limiting use for 2- to 5 year olds to just one hour a day of "high-quality programming," and even then watching it with them so you can support learning.

Watching beyond this amount could have lasting effects on your child's health, even harming brain development, according to a study by researchers at Cincinnati Children's Hospital Medical Center. Those with greater screen time had "lower microstructural integrity" of brain white matter, an area linked with cognitive function and language.

Excess Screen Time Changes Preschoolers' Brains

The study involved 47 children between the ages of 3 and 5. ScreenQ was used to measure screen usage in accordance with AAP recommendations, taking into account such factors as access to screens, frequency of use, what type of content was viewed and whether coviewing occurred --as in, did an adult watch along with the child and discuss the content?

A higher ScreenQ score was associated with greater screen time. MRIs were then used to assess the children's brains, revealing that more screen time was harmful to the brain's white matter, particularly in tracts supporting language and literacy skills.

"While we can't yet determine whether screen time causes these structural changes or implies long-term neurodevelopmental risks," Dr. John Hutton, director of the Reading & Literacy Discovery Center at Cincinnati Children's and lead study author said in a news release, "these findings warrant further study to understand what they mean and how to set appropriate limits on technology use."

A number of recent studies have highlighted the risks of too much screen time for preschoolers. A Canadian study suggested preschool children spend an average of two hours using screens daily, and those who spent more than this amount had a 7.7-fold higher risk of meeting criteria for attention-deficit hyperactivity disorder (ADHD).

Among even younger 18-month-old children, those who were allowed to view media on mobile devices were more likely to have expressive speech delays, with each additional 30 minutes of viewing time associated with greater odds of a speech delay. AAP recommends toddlers younger than 18 to 24 months avoid digital media, except for video chatting.

Limit or Avoid Screen Time for Children's Health

Researchers are only beginning to understand the many ways that screen time interferes with human health. Beyond your brain, staring at screens is damaging for eyesight and comes with the risks of exposure to electromagnetic fields (EMFs), Wi-Fi radiation and other threats of cellphone exposure

There's also the fact that most screen time occurs while sitting down, cutting down on physical activity and increasing the risks of prolonged sitting time -- a health risk in itself.

There's no need to wait for more definitive research before taking action to protect children's health. Use AAP's screen time guidelines as a maximum, and even better reduce your child's screen time, including television viewing, as much as possible, or eliminate it completely, especially in their early years. 

It's also a good idea to establish screen-free times and activities for your family. Even as your children enter their teen years, ensure that meal times, bed time and other times you designate are free from any digital distractions.

Some school environments, such as Waldorf, exclude all technology from their classrooms and their student's curriculum. They also encourage the same standards for the children at home. This is increasingly becoming a healthy option for concerned parents who are aware of the growing number of unintended, adverse effects of EMF associated technologies. For more information on EMF harms, visit the GreenMedInfo database on Electromagnetic Fields, which contains over 1,000 studies linking EMF to over 140 different adverse health effects.


[1] American Academy of Pediatrics May 1, 2018

[1] JAMA Pediatrics November 4, 2019

[1] Science Daily November 4, 2019

[1] PLOS One April 17, 2019

[1] J Dev Behav Pediatr. 2019 Feb-Mar; 40(2): 99-104.

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