A study published in the journal JAMA Pediatrics found that the teens who spend too much time on social media or watching television become notably more depressed.

The six-year study tracked over 3,800 students in Montreal, asking them to track (in class) both how much time per day they had spend watching TV, browsing social media and playing video games. As part of the same survey, they were asked to measure their level of depressive symptoms, such as loneliness and sadness.

An increase of as little as one hour of social media interaction from normal levels would result in a measurable increase in depression, the study found. (Researchers found no correlation, it’s worth noting, between signs of depression and video games.)

“We found an association between social media and depression in adolescence,” reads the report. “Based on the upward social comparison, it may be that repeated exposure to idealized images lowers adolescents’ self-esteem, triggers depression, and enhances depression over time. Furthermore, heavier users of social media with depression appear to be more negatively affected by their time spent on social media, potentially by the nature of information that they select.”

Several previous studies have linked social media and depression, but this is seemingly the first long-term one to focus exclusively on teens. While the JAMA study did not tie screen time to increased suicides, they did note that depression during adolescence has been linked to teens taking their own lives.

The authors acknowledge their study has limitations, such as not determining which types of social media and which genres of television exacerbate depressive symptoms. However, they note, “adolescents’ social media and television use should be regulated to prevent the development of depression and to reduce exacerbation of existing symptoms over time.”