Anything more than one hour a day of screen time may correlate with increased rates of depression and anxiety in teens.

Young people who spend seven or more hours a day looking at screens are twice as likely as their peers who have only one hour of screen time to develop depression or anxiety. That's the conclusion of a recently published study conducted by researchers at San Diego State University. The researchers made this conclusion by evaluating data from the Census Bureau's 2016 National Survey of Children’s Health, which surveyed 40,000 children from ages of two to 17.

While the younger kids in the survey rarely achieved such high levels of screen time, nearly 20 percent of respondents in the 14 to 17 age bracket did. And in this group, the correlation between screen time and poor mental health were the highest. Teens who spent seven hours or more in front of screens experienced the greatest impacts, but the negative effects of screen time were also noted in lesser degrees in young people who used screens for four hours a day. Jean Twenge, the study's lead author, says the reason why screen time seems to affect teens more than younger children likely has to do with the kinds of on-screen activities they're doing.

"Teens spend more time on their phones and on social media, and we know from other research that these activities are more strongly linked to low wellbeing than watching TV and videos, which is most of younger children's screen time," she explained to Time.

Twenge believes that the findings of her study proves there should be more aggressive limits on young people's screen time.

"At the moment, the American Academy of Pediatrics (AAP) guidelines set specific time limits on screen time only for children [ages] five and younger," she says. "These findings and others suggest the AAP should consider extending these specific limits to older children and adolescents."

However, not everyone agrees with the conclusions Twenge has drawn from the data. Andrew Przybylski, an associate professor and director of research at the Oxford Internet Institute at the University of Oxford, published a similar study based on older Census Bureau data a few years ago. He believes Twenge's proposed limits of screen time are unwarranted, noting that we don't know if screen time leads to depression or the other way around.

"For the research [in this] area to mature, people need to sort out these factors before making expansive claims."

And Przybylski is probably right. We'll need some more research before we know for sure how generalized increases in screen time are affecting the mental health of young people. However, it is clear that screen time is increasing rapidly, and social media in particular seems to do more harm than good.