More than twice as many young people watch videos every day as did four years ago, and the average time spent watching videos — mostly on YouTube — has roughly doubled, to an hour each day.

That’s according to a survey released Tuesday by Common Sense Media, a nonprofit that tracks young people’s tech habits. The report found that overall screen time among young people hasn’t changed much since 2015. On average, American 8-to-12-year-olds spent 4 hours and 44 minutes on screen media each day. And teens average 7 hours and 22 minutes — not including time spent using screens for school or homework.

But usage has surged despite mounting concerns from parents and consumer groups about the grip that smartphones and screens have on kids’ lives and development. Advocates worry that features hard-wired into certain tech platforms, such as YouTube’s default autoplay setting, reinforce the impulse to keep watching.

“More and more screen time is devoted to content that’s been picked for you by an algorithm,” said Michael Robb, a co-author of the study and senior director of research for Common Sense Media. “And then there’s more individualized uses of media on a personal device, rather than a family sitting together.”

For comparison, Common Sense Media found that in 2015, watching online videos ranked fifth in terms of tweens’ preferred media activities — after TV, music, video games and mobile games. Today, online videos claim the top spot.

Limiting screen time for young people is a rallying cry not only among consumer advocates but also among global health communities. In April, the World Health Organization issued strict guidelines on how often parents should turn to videos and online games to entertain or educate their children.

The WHO’s recommendation: Infants younger than 1 should never be in front of screens. Kids ages 2 to 4, the international health agency said, should have no more than an hour each day of sedentary screen time.

YouTube, which has a global audience of more than 2 billion people, launched YouTube Kids in 2015. The company has information for parents with tools for how to navigate its site with teenagers. The company said that accounts of people younger than 13 are terminated if discovered and that thousands of accounts per week are shut down for this reason. The company also said parents watching with young people may opt for YouTube’s restricted mode, which helps screen out certain content.

“YouTube Kids is our experience designed for kids from the ground up and is what we recommend if parents want their kids to watch independently. YouTube is not a site for people under 13,” said Farshad Shadloo, a spokesman for YouTube.

Consumer groups caution that despite promises to police inappropriate content, YouTube continues to show violent imagery, drug references, racist language and sexually suggestive content that reaches children. Robb said the percentage of young people surveyed who said they used only YouTube Kids, as opposed to the broader site, was tiny.

The Common Sense Media report pulled from a national survey of more than 1,600 American 8-to-18-year-olds about their use of, and relationship with, different types of media. Tweens were defined those ages 8 to 12, and teenagers as those ages 13 to 18. The report also found that by age 11, most kids — 53 percent — have their own smartphone. That figure rises to 69 percent by the time they’re 12.

Young people also spent relatively little time creating their own content or interacting with others while on their screens. Among tweens, slightly more than half of all screen use was dedicated to TV or videos, and 31 percent went to gaming. Video chatting, reading online, or creating content like art or music each accounted for 2 percent.

Common Sense Media plans to release a similar study in another four years. But James Steyer, the organization’s founder and chief executive, said there was much more urgency for tech companies and federal regulators to respond. Steyer — who is the brother of Democratic presidential candidate Tom Steyer — said children’s screen time has wide-ranging implications for their social and emotional development, how they form relationships, how they identify themselves, and how they are exposed to extreme politics, hate speech and conspiracy theories.

“This is central to the fabric of our lives,” Steyer said, “and particularly to our kids’ lives.”