Scientists are divided on the health benefits of a dozy afternoon, reports Popular Science.

Here’s your new naptime mantra: “Keep it brief.” While everyone you know swears by a certain magic number (7 minutes! No, 17 minutes!), the National Sleep Foundation has this to say: “a short nap”—say, 20 minutes—“can help to improve mood, alertness and performance,” without side effects like grogginess.

When you lie down for those 20 minutes of shuteye, even if you’re really tired, it can be hard to actually fall asleep.