The new study indicates that more hours of screen time are associated with lower well-being in those aged 2 to 17, though the association is larger for adolescents than for younger children

Too much time spent on gaming, smartphones and watching television is linked to heightened levels and diagnoses of anxiety or depression in children as young as age 2, according to a new study.

Even after only one hour of screen time daily, children and teens may begin to have less curiosity, lower self-control, less emotional stability and a greater inability to finish tasks, reports San Diego State University psychologist Jean Twenge and University of Georgia psychology professor W. Keith Campbell.

Twenge and Campbell's results were published in an article, "Associations between screen time and lower psychological well-being among children and adolescents: Evidence from a population-based study," which appeared this month in Preventative Medicine Reports.

Twenge and Campbell were particularly interested in associations between screen time and diagnoses of anxiety and depression in youth, which has not yet been studied in great detail.

Their findings provide broader insights at a time when youth have greater access to digital technologies and are spending more time using electronic technology purely for entertainment, and also as health officials are trying to identify best practices for managing technology addiction.

"Previous research on associations between screen time and psychological well-being among children and adolescents has been conflicting, leading some researchers to question the limits on screen time suggested by physician organizations," Twenge and Campbell wrote in their paper.

The National Institute of Health estimates that youth commonly spend an average of five to seven hours on screens during leisure time. Also, a growing body of research indicates that this amount of screen time has adverse effects on the overall health and well-being of youth.

Also timely: the World Health Organization this year decided to include gaming disorder in the 11th revision of the International Classification of Diseases. The organization is encouraging "increased attention of health professionals to the risks of development of this disorder" as gaming addiction may now be classified as a disease.

Utilizing National Survey of Children's Health data from 2016, Twenge and Campbell analyzed a random sample of more than 40,300 surveys from the caregivers of children aged 2 to 17.

The nationwide survey was administered by the U.S. Census Bureau by mail and online and inquired about topics such as: existing medical care; emotional, developmental and behavioral issues; and youth behaviors, including daily screen time. Twenge and Campbell excluded youth with conditions such autism, cerebral palsy and developmental delay, as they may have impacted a child's day to day functioning.

Twenge and Campbell found that adolescents who spend more than seven hours a day on screens were twice as likely as those spending one hour to have been diagnosed with anxiety or depression - a significant finding. Overall, links between screen time and well-being were larger among adolescents than among young children.

"At first, I was surprised that the associations were larger for adolescents," Twenge said. "However, 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 well-being than watching television and videos, which is most of younger children's screen time."

Among other highlights of Twenge and Campbell's study:

Moderate use of screens, at four hours each day, was also associated with lower psychological well-being than use of one hour a day.

Among preschoolers, high users of screens were twice as likely to often lose their temper and 46 percent more likely to not be able to calm down when excited.

Among teens aged 14-17, 42.2 percent of those who spent more than seven hours a day on screens did not finish tasks compared with 16.6 percent for those who spent one hour daily and 27.7 percent for those engaged for four hours of screen time.

About 9 percent of youth aged 11-13 who spent an hour with screens daily were not curious or interested in learning new things, compared with 13.8 percent who spent four hours on screen and 22.6 percent who spent more than seven hours with screens.

The study provides further evidence that the American Academy of Pediatrics' established screen time limits - one hour per day for those aged 2 to 5, with a focus on high-quality programs - are valid, Twenge said.

The study also suggests that similar limits - perhaps to two hours a day -- should be applied to school-aged children and adolescents, said Twenge, also author of "iGen: Why Today's Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy--and Completely Unprepared for Adulthood."

In terms of prevention, establishing possible causes and outcomes of low psychological well-being is especially important for child and adolescent populations. "Half of mental health problems develop by adolescence," Twenge and Campbell wrote in their paper.

"Thus, there is an acute need to identify factors linked to mental health issues that are amenable to intervention in this population, as most antecedents are difficult or impossible to influence," they continued. "Compared to these more intractable antecedents of mental health, how children and adolescents spend their leisure time is more amenable to change."

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