Screen time for U.S. tweens and teens during the COVID-19 pandemic skyrocketed, a new study suggests. 

Researchers looked at how many hours per day adolescents spent streaming, texting, gaming, video chatting, on social media or browsing the internet.

They found that, prior to the pandemic, youngsters had about fours per day of screen time. But, with schools closed and stay-at-home orders in place, this rose to nearly eight hours per day.

What's more, males, African Americans, those living in household with incomes below $75,000 and those with parents who never attended college had the most hours of screen time.

The team - from the University of California, San Francisco; the University of California, Los Angeles; the University of Toronto in Canada; and SRI International - says this increased screen time doesn't just affect physical health, such as worsening vision, but is also associated with mental health risks. 

When the COVID-19 pandemic struck last year, lockdowns and stay-at-home mandates shut down schools.

Kids suddenly went from using screens not just for entertainment and socializing but also for online learning.

But, additionally, they were able to spend time using screens before and after attending remote lessons. 

Several studies have found that children and teenagers were getting more screen time, but none using national U.S. data.