Here’s one more reason to limit your child’s time in front of a screen. Social media could be reprogramming children’s brains and making them hooked on “likes,” a new study from the University of North Carolina reveals.

Experts say that apps such as Instagram or Snapchat could be making teenagers constantly check their phones to see if they have positive or negative reactions to their online posts. Psychologists believe that the more young people check social media, the more sensitive they become to “social feedback” in the form of likes and comments.

Social feedback includes rewards and punishments such as thumbs up and down, tagging, reporting content or star ratings. According to researchers, this increasing anticipation and sensitivity to receiving these kinds of responses make it hard for adolescents to fight the urge to check their accounts.

“Our findings suggest that checking behaviors on social media in early adolescence may tune the brain’s sensitivity to potential social rewards and punishments,” their paper, published in JAMA Pediatrics, explains. “Individuals with habitual checking behaviors showed initial hypoactivation but increasing sensitivity to potential social cues over time, those with non-habitual checking behaviors showed initial hyperactivation and decreasing sensitivity over time.”

During adolescence, the brain experiences “significant structural and functional reorganization changes,” making it a crucial development period. “Neural regions involved in motivational relevance and affective become hyperactive, orienting teens to rewarding stimuli in their environment, particularly from peers,” the authors say.

The researchers studied 169 students from three public middle schools in North Carolina over three years. Each participant reported how often they checked the popular social media platforms Facebook, Snapchat and Instagram. Some admitted to doing so more than 20 times a day. They also participated in a Social Incentive Delay task where their brain responses were measured when they were anticipating receiving social rewards and avoiding social punishments.

Previous research shows that 78 percent of 13 to 17-year-olds report checking their devices at least hourly daily, and 35 percent look at the top five networks “almost constantly.” In this study, the authors point out that students who look at social media at least 15 times daily were the most sensitive to social feedback. “The findings suggest that children who grow up checking social media more often are becoming hypersensitive to feedback from their peers,” says Eva Telzer, a professor in UNC-Chapel Hill’s psychology and neuroscience department and a corresponding author, in a statement. ”

“Social media platforms provide adolescents with unprecedented opportunities for social interactions during a critical developmental period when the brain is especially sensitive to social feedback,” the study concludes. This longitudinal cohort study suggests that social media behaviors in early adolescence may be associated with changes in adolescents’ neural development, specifically neural sensitivity to potential social feedback.

“Further research examining long-term prospective associations between social media use, adolescent neural development, and psychological adjustment is needed to understand the effects of a ubiquitous influence on development for today’s adolescents,” they add. A National Institutes of Health grant and the Winston Family Foundation supported the study.