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."
