The Science Behind Screens and Sleep Disruption

If you've ever read anything about sleep science, you've probably heard that screens before bed are a big no-no.

And if you're anything like me, you’ve probably ignored that advice. Because, well—come on.

Even sleep researchers can’t always resist.

Do you use your phone before bed?

"Yes," says Rohan Nagare, a sleep researcher who's coauthored multiple studies on the topic.

"I check my calendar and emails—never more than 30 minutes."

As someone who also regularly scrolls before sleep, I wanted to find out: Is there a way to keep using our phones at night without totally messing up our sleep?

Turns out, the science suggests that our sleep patterns are more flexible than we might think.

But first, a quick refresher on how our bodies respond to light—especially natural light.

You've probably noticed that you start to feel sleepy as night falls. That’s due to melatonin, a hormone that plays a crucial role in sleep. But melatonin is more than just a sleep trigger—it's an internal clock that helps regulate your entire circadian rhythm.

When the sun rises and you’re exposed to bright light, your body suppresses melatonin production, helping you wake up and feel alert.

And it’s not just about brightness—the color temperature of light matters, too.

Daylight sits at around 5600 Kelvin, which is on the blue end of the spectrum.

As the sun sets, the light shifts warmer—closer to 3000 Kelvin—which signals your body to start producing melatonin again.

This gradual transition from bright blue light to dim, warm tones helps your body naturally prepare for sleep.

So far, so good.

But then we add artificial light into the mix—especially from screens—and things get tricky.

Most phone screens emit light at a color temperature of around 5600K: basically, artificial daylight. That’s why you often hear that screen use at night disrupts sleep—it mimics daylight and suppresses melatonin.

But wait—don’t our phones have features like Night Shift or Night Mode that reduce blue light?

Yes, they do. But do they actually work?

In 2019, Rohan coauthored a study to explore that exact question.

"It's a clever idea," he says. "They’re trying to adjust the screen's spectrum to reduce its impact on the circadian system."

The study tested two types of "warm shift" modes:

• High CCT: a strong shift to warmer colors

• Low CCT: a slight warm tint

Both modes still suppressed melatonin. And neither one showed a meaningful difference in terms of reducing disruption.

At first glance, it might sound like Night Shift is ineffective—but the reality is more nuanced.

Spectrum (color temperature) is just one factor.

Other variables—like timing, duration, light intensity, and exposure distribution—also matter a lot.

"If you're on your phone for 20 to 30 minutes, I wouldn’t worry too much," Rohan says.

"But if you’re watching a movie or bingeing a few episodes every night? That builds up a pretty solid ‘circadian dose’ and delays your sleep cycle."

Another key factor? Distance.

When you’re holding your phone close to your face, your eyes are getting hit with more concentrated light. Light intensity, measured in lux, increases dramatically the closer you are to the source.

In fact, light from a source held at half the distance appears four times more intense.

So even if your screen is set to warm tones, if it’s cranked up to full brightness and held close to your face, it can still overwhelm your circadian system.

Bottom line?

Reducing screen time, lowering brightness, and enabling warm shift modes all help—but they’re only part of the solution.

Rohan also shared an interesting circadian hack:

What really matters is the contrast between the light you get right after waking up and the light exposure right before bed.

"If you’re going to bump your screen brightness from 50 lux to 200 lux at night," he says,

"you can offset that by getting 800 lux or more in the morning. A sunny walk does wonders."

In other words, you can trick your internal clock by making sure you get a strong dose of morning light to counteract your nighttime screen habits.

At the end of the day, blue light isn’t the only factor messing with our sleep.

What you do on your phone—like doom-scrolling, reading stressful news, or watching horror movies—can be just as stimulating as the light itself.

The real takeaway?

If we want healthier sleep, we need a healthier relationship with our screens. And that starts with understanding how our habits, not just our devices, shape our rest.

Thanks for reading.