LOS ANGELES (CBSLA) — Young people using digital devices heavily are more prone to symptoms of ADHD, a study out of USC has found.

After narrowing down its study group to more than 2,500 Southern California-area high school students with no preexisting ADHD symptoms, researchers from USC, UCLA and UC San Diego found over two years that even medium use of digital media platforms led to an increase of new ADHD symptoms.

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“We can’t confirm causation from the study, but this was a statistically significant association,” USC professor Adam Leventhal said in a statement. “We can say with confidence that teens who were exposed to higher levels of digital media were significantly more likely to develop ADHD symptoms in the future.”

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ADHD, or attention-deficit/hyperactivity disorder, is described as a brain disorder that includes a pattern of inattention, hyperactive behavior and impulsiveness that interferes with functioning or development.

The CDC says 43 percent of high school students use digital media three or more hours a day, while a survey by Common Sense Media showed teens spend nearly nine hours of their day on online media. The constant stimulation from digital devices is different from the effects of TV or video games on young people’s attention spans.

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“New, mobile technologies can provide fast, high-intensity stimulation accessible all day, which has increased digital media exposure far beyond what’s been studied before,” Leventhal said.