Teenagers who constantly use their smartphones may have a heightened risk of developing symptoms of attention-deficit/hyperactivity disorder, a new study suggests.
The findings offer a look at a question many parents may have: Can those ubiquitous digital devices -- and their constant pull on kids' attention -- cause mental or behavioral issues?
The answer, the study authors said, is "maybe."
The researchers found that teens who used their devices "many times" a day were at increased risk of developing attention-deficit/hyperactivity disorder (ADHD) symptoms over the next two years.
Around 10 percent reported new problems with attention, focus or being still, which are hallmarks of ADHD. That compared with less than 5 percent of their peers who kept their device use to a minimum.
But the findings do not prove that digital media are to blame, said Dr. Jenny Radesky, who wrote an editorial published with the study.
There are many other factors that could affect teenagers' likelihood of reporting those symptoms, said Radesky, an assistant professor of pediatrics at the University of Michigan.
The researchers accounted for the factors they could -- such as family income and whether kids had depression symptoms, smoked or used drugs or alcohol at the outset.
But there were things the researchers couldn't measure, Radesky said.
A key missing piece, she said, is how parents influenced their kids. Teens who were not glued to their phones might have had parents who set more rules at home -- or encouraged their kids to have "positive activities" that fostered their mental development.
That said, Radesky called the study important.
"It's one of the first to be able to look at this question longitudinally," she said, meaning it followed the same group of teens over time.
So, it was able to show that the higher rate of ADHD symptoms came after -- not before -- the heavy device use.
Media distractions -- from TV to music to video games -- are nothing new. But mobile technology is different, said lead researcher Adam Leventhal.
"It's the unrelenting access and constant engagement throughout the day," said Leventhal, a professor at the University of Southern California Keck School of Medicine, in Los Angeles.
The findings were published July 17 in the Journal of the American Medical Association.