Exposure to all colors of light helps control your natural sleep-and-wake cycle, or circadian rhythm. More so than any other color, blue light messes with your body's ability to prepare for sleep because it blocks a hormone called melatonin that makes you sleepy.

Can blue light affect your sleep?

Light therapy, and blue light in particular, can help realign the body's circadian rhythms and improve sleep. Blue light suppresses the body's release of melatonin, a hormone that makes us feel drowsy. While this may be helpful during the day, it becomes unhelpful at night when we're trying to sleep.

How does blue light from phones affect sleep?

The blue light emitted by your cell phone screen restrains the production of melatonin, the hormone that controls your sleep-wake cycle (aka circadian rhythm). This makes it even more difficult to fall asleep and wake up the next day.