An alarming new study finds that kids who use smartphones or other devices with screens may have major issues with sleep and nutrition. Researchers at Penn State College of Medicine found that children between the ages of 8 and 17 were more likely to sleep less and experience much poorer quality of sleep if they were addicted to their screens.

The survey, sent to 234 parents, also indicated that using cell phones or watching TV before bed was associated with a higher body mass index (BMI). Researchers believe this is because kids were more likely to skip breakfast if they were tired in the morning, and skipping the first meal of the day is a major factor in obesity.

Specifically, kids who got a lot of screen time via TVs or video games before bed slept 30 minutes less on average, and it was even worse for smartphones, with those kids averaging a full hour less sleep.

“It may be tempting to let your kids stay up late playing games on their smartphones, but using digital devices before bed may contribute to sleep and nutrition problems in children, according to Penn State College of Medicine researchers,” reads a statement from the university. “After surveying parents about their kids’ technology and sleep habits, researchers found that using technology before bed was associated with less sleep, poorer sleep quality, more fatigue in the morning and –in the children that watched TV or used their cell phones before bed — higher body mass indexes (BMI).”