Children younger than a year old shouldn’t be exposed to any electronic screens, according to guidelines issued Wednesday by the World Health Organization.

The United Nations agency, issuing its first such guidelines, also recommended that children ages 2 to 4 have no more than one hour of “sedentary screen time” — including playing computer games or watching TV — per day. It emphasized that young kids need be physically active and get enough sleep, habits that go a long way in preventing obesity and other diseases later in life.

"Achieving health for all means doing what is best for health right from the beginning of people's lives," WHO Director-General Tedros Adhanom Ghebreyesus said in a statement. "Early childhood is a period of rapid development and a time when family lifestyle patterns can be adapted to boost health gains."

The action comes amid growing research into the developmental effects of the widespread use of computers and mobile devices by children. One concern is that the mesmerizing effects of videos keep young children from connecting with their parents and others, a key facet in building the sophisticated social skills that are central to human development.

Surveys have consistently shown that children have been exposed to rising amounts of screen time in recent years, including by parents struggling with the challenges of managing the moods and time demands of young children. Many of the most popular channels on YouTube, for example, feature nursery rhymes, simplistic games and other content that appeal to preschoolers. (YouTube long has maintained that its service is intended for those 13 or older.)

"It's extraordinarily important that someone with the authority and reach of the WHO is saying this," said Josh Golin of the Campaign for a Commercial Free-Childhood, an advocacy group based in Boston. He said of screen time for children, "It's not essential to learning, and it's not effective at teaching."

Golin also said that studies show worrying signs of possible developmental effects on the ability of children to acquire language and social skills. Even the use of mobile devices by parents can affect their children by distracting mothers and fathers from the routine interaction young minds crave, he said.

The WHO guidelines vary somewhat from the recommendations of the American Academy of Pediatrics in 2016. At the time, the AAP said that infants and toddlers younger than 18 months should only be in front of screens to video-chat with people their parents approve of. Educational shows could be introduced to kids 18 to 24 months old, but the AAP emphasized that parents should “prioritize creative, unplugged playtime for infants and toddlers.”

Babies should not be exposed to screens at all and instead engage in interactive floor-based play, the WHO said. It also recommended that kids ages 1 to 4 have at least three hours of physical activity daily.

Concerns about children and screen time began well before kids starting reaching for their parents’ iPads and smartphones, said Emily Oster, a professor of economics at Brown University and the author of “Cribsheet: a Data-Driven Guide to Better, More Relaxed Parenting.” But there isn’t yet enough compelling evidence, Oster said, tracking the effects of screens beyond a household television. Kids who grew up around iPads, for example, aren’t old enough for researchers to measure their educational or developmental growth.

Parents ultimately face choices, Oster said.

Article continues below

“I think people need to look at this and think about the fact that these guidelines are not based on some underlying, well-rehearsed truth and use their judgment to decide what’s going to work,” Oster said. “These ideas that kids are going to be physically active and get enough sleep — that’s a good idea, but it’s not all about screens.”

There has been a push in recent years to study what some experts call the "addictive" effects of some technologies, especially social media and online services such as YouTube that automatically play one video after another. Sen. Edward Markey, D-Mass., and a bipartisan group of lawmakers have proposed legislation calling for the National Institutes of Health to conduct a $40 million, multiyear study of the effect of technology, screen time and online media on infants and other children.

"It's important to make sure kids aren't spending too much time in front of screens, but we need a comprehensive national discussion about how to ensure children and teens' health and wellness as their technology use increases," Markey said in a statement after the release of the WHO guidelines Wednesday. "Public policy and parenting best practices should be informed by robust research into the cognitive, physical, and socio-emotional effects of kids' digital media consumption. I've introduced bipartisan legislation tasking NIH to gather these facts, so we can chart an evidence-based path forward."

Inadequate physical activity is directly linked to more than 5 million deaths worldwide, across all age groups, in a given year, according to the WHO. Nearly one-quarter of adults, and 80 percent of adolescents, aren’t active enough — and learn harmful habits early in life.

There's an important difference between "screen time" and "screen use" said Stephen Balkam, founder and chief executive of the Family Online Safety Institute, who members including major technology industry players such as Google, Facebook and Amazon.