Birken said more research is needed to determine what content the children are viewing, and also whether they are using the devices with a parent or caregiver present, CNN reported.
"I think in order to actually develop the evidence to inform parents and clinicians about what to recommend, we need more definitive research," Birken said. "You need trials. You need good evidence, at least longitudinal studies, but this, at least, this finding is identifying an association and it does support the current recommendation" from the American Academy of Pediatrics.
That group recommends no screens at all, other than video-chatting with family, for children younger than 18 months, CNN reported.
For kids between the ages of 18 to 24 months, the American Academy of Pediatrics recommends that parents choose high-quality programming and watch it with their children to help them understand what exactly they are seeing.
Nearly 40 percent of children under age 2 have used a mobile device, an increase of 10 percent in 2011, according to a 2013 study by Common Sense Media.