Here's What Blue Light Before Bed Can Do to Your Circadian Rhythm — and How to Avoid It

Blue light is processed by special photoreceptors in your eyes, which in turn stimulate different parts of your brain, according to Mark Wu, MD, PhD, an associate professor of neurology at Johns Hopkins who specializes in sleep and circadian rhythm disorders. One affected area is called the suprachiasmatic nucleus (SCN), which is responsible for regulating your circadian rhythm, the internal clock that keeps you going to bed and waking up at the same times.

"If you expose yourself to blue light at night, what it can do is shift your clock later," Dr. Wu told POPSUGAR. "It would make you want to go to bed later and then wake up later, which obviously is not ideal for lots of working people." In other words, if you're habitually on your phone or laptop late at night, it can trick your body into thinking it's daytime, keeping you alert and awake when you'd usually start to get sleepy.

"Generally, this is not likely to happen after just one night," said Luis Buenaver, PhD, an assistant professor and director of the Behavioral Sleep Medicine Program at Johns Hopkins's department of psychiatry and behavioral sciences. "But [it] may become an issue after several nights or if it becomes a bad habit."

Relatedly, melatonin is a hormone that regulates your circadian rhythm. Blue light actually can neutralize the effects of your naturally occurring melatonin, which is "usually secreted about two hours prior to one's habitual bedtime," Dr. Buenaver explained. Too much exposure to blue light can throw off that routine and keep your brain on high alert, making it difficult to fall asleep or sleep soundly once you do drift off.

On top of disrupting your circadian rhythm and melatonin production, blue light also directly stimulates the part of your brain that makes you feel awake, Dr. Wu said. That can be a good thing during the day, but "it's not something you want when you're trying to go to bed," he explained.

That's especially important because, even beyond blue light, using your phone or computer before bed will naturally make you feel more alert. If you're reading or watching something that gets you worked up in some way, it's going to be hard to drift off. "You get either excited or upset, and that's not conducive to sleep," Dr. Wu said. When you put together that natural stimulation with the physical effects of blue light on your brain, hormones, and circadian rhythm, you get a combination that's highly likely to disrupt your sleep.

Dr. Wu and Dr. Buenaver suggested a few ways to deal with the sleep issues created by blue light. If you find yourself mindlessly scrolling Instagram or clicking yet another video as it gets closer to bedtime, try a few of these techniques to keep your sleep cycle on track: