MENLO PARK, Calif. (CBS Sacramento) — A new study finds that 20 percent of teenagers wake up during the night to check their Facebook.

According to the Irish Mirror, researchers found that teens waking up in the middle of the night to use Facebook or other social media sites are leaving them tired at school.

The study also found that more than a third of those aged 12 to 15 wake up at least once a week to check or post messages.

“It seems important to discourage social media use during the night,” Dr. Kimberly Horton, of the Wales Institute of Social and Economic Research, Data and Methods, told the Irish Mirror. “No effort to develop regular bedtimes or lengthen time in bed would compensate for the disruption nighttime use can cause.”