Most of us are glued to our smartphones 24/7, but that definitely isn’t a good thing—especially when it comes to getting to sleep.

Cellphones and other electronic devices like laptops and tablets emit blue light. Blue light delays the body’s natural release of melatonin, a hormone that regulates the sleep-wake cycle. Blue light makes us feel more alert and disturbs our body’s natural, internal clock, or circadian rhythm.  As a result, using electronic devices before bed makes us feel more awake and makes it more difficult to fall asleep.

It’s best to avoid staring at your smartphone screen in the two hours before you plan on going to sleep. Ordinarily, the brain releases melatonin two hours before bedtime to signal to the body that it’s time to rest. Using electronic devices that emit blue light during this time can mess with your melatonin levels and make it a whole lot harder to fall asleep.