Why Do Screens Keep You Up? It May Not Be the Blue Light.
But the link between blue light and sleep is murkier than we thought, said Lauren E. Hartstein, an assistant professor of psychiatry at the University of Arizona. She and other researchers have been taking a closer look at the evidence, which suggests that blue light alone may not be causing poor sleep. And in some cases, screen use could even help you drift off.
Here's what studies on blue light actually suggest — and what may help you sleep more soundly.
Research on blue light and sleep is mixed.
Many of the available studies on blue light and sleep are old and are limited by their small sample sizes. They were also often performed in carefully controlled laboratories, so their results don't always reflect real life, Dr. Hartstein said.
While it's true that blue light exposure can sink melatonin levels, the limited evidence we have suggests that screen use does not always cause this dip, said Mariana Figueiro, a scientist at the Icahn School of Medicine at Mount Sinai in New York City who studies how light influences health.
Some of Dr. Figueiro's research suggests, for instance, that how long you use your device for, how close it is to your eyes and how bright it is may play a role. One of her studies from 2013 found that using an iPad at full brightness for two hours caused melatonin levels to drop slightly, whereas using it for one hour caused no change. Another study from 2014 concluded that watching television from nine feet away had no effect on melatonin levels. And using an iPad at a higher brightness level may suppress melatonin more than using it at a lower brightness level, according to a 2018 study.
What you do during the day may also influence screen-related melatonin drops at night. The more bright sunlight you're exposed to during the day, some research suggests, the less susceptible you may be to an evening dip.
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