Blue Light May Not Be Keeping You Up at Night

For years, experts warned that blue light from phones and laptops could ruin your sleep. But new research suggests the truth may be more complicated — and less alarming.

Rethinking the Science

Blue light, a short-wavelength light emitted by screens, has been thought to suppress melatonin, the hormone that regulates the sleep-wake cycle. That’s why the National Sleep Foundation and others have long advised avoiding screens before bed.

But studies now show the effects aren’t the same for everyone. “The research on blue light and sleep is mixed,” says Lauren E. Harstein, assistant professor of psychiatry at the University of Arizona, according to the New York Times.

Timing and Sensitivity Matter

Mariana Figueiro, director of the Light and Health Research Center at Mount Sinai, has found that the impact of blue light depends on when, how bright, and how sensitive you are.

Daytime exposure to blue-rich light can boost alertness and mood.

Late-night exposure, especially from bright screens held close to the face, may delay melatonin and disrupt sleep in sensitive individuals.

Brightness is key. Figueiro’s studies show dimming devices can reduce or eliminate melatonin suppression. Watching TV from a distance, for example, often has no effect.

Not Everyone Reacts the Same

A 2019 study of 55 adults found dramatic differences: one person needed 40 times more blue light than another to see a drop in melatonin. Similarly, a 2022 review of multiple studies found mixed results—some showed no effect, one even suggested improved sleep quality.

More Than Just the Light

Harstein notes that what you do on your device may matter more than the light itself. Stimulating activities—like video games, social media, or online shopping—can keep your brain revved up even after you shut the screen.

“The device can turn off, but your brain can’t,” she says.

The Bottom Line

If screens seem to interfere with your sleep, experts recommend lowering brightness, keeping devices at a distance, and giving yourself some buffer time before bed. But if your nightly scrolling doesn’t disrupt your rest, there’s little need to worry.