Must... Have... Sleep (IMAGE) Brown University Caption Light from device screens -- even the old reading under the covers with a flashlight tactic -- in the hour before bed can significantly disrupt sleep time. The effect is more pronounced in younger tweens and teens, ages 9 to 15. Credit Mike Cohea/Brown University Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.