Key Takeaways
- Blue light does suppress melatonin—but the effect from screens is smaller than you've been told
- A 2019 study found screen blue light delays melatonin by only ~3-6 minutes on average
- Light intensity matters more than light color—bright white light is worse than dim blue light
- Blue light blocking glasses have weak evidence for sleep improvement
- What you're doing on your device matters more than the light it emits
Walk into any pharmacy and you'll find $100 blue light blocking glasses promising better sleep. Open Instagram and influencers swear their blue blockers changed their lives. Phone manufacturers now ship with "night mode" as a prominent feature.
There's just one problem: the science behind all this isn't as clear-cut as the marketing suggests.
Don't get me wrong—blue light affects sleep. That's real. But the magnitude of the effect, the solutions being sold, and what actually matters? That's where things get interesting. I spent way too many late nights (ironic, I know) digging through the research. Here's what I found.
01 The Claims You've Heard
The narrative goes something like this: Blue light from screens suppresses melatonin production, delaying your sleep and disrupting your circadian rhythm. Therefore, blue light blocking glasses and night mode settings are essential for good sleep.
What Companies Tell You
The reality is more nuanced. Let me explain.
02 What the Science Actually Says
Blue Light Does Affect Melatonin—But How Much?
Yes, your retina contains cells called intrinsically photosensitive retinal ganglion cells (ipRGCs) that are particularly sensitive to blue wavelengths (around 480nm). These cells signal to your brain's master clock about light exposure[1].
The key studies that sparked the blue light panic used bright laboratory light— much brighter than a typical screen. When researchers looked specifically at screens at realistic distances and brightness levels, the effects were much smaller.
"The amount of light coming from screens is fairly small compared to what we get from the environment."
— Dr. Cathy Goldstein, University of Michigan Sleep Medicine
The Studies That Changed the Picture
Screen Blue Light Effect Size
A carefully controlled study at BYU measured actual melatonin suppression from phone use before bed. The result? Blue light from phones delayed melatonin onset by an average of 3.8 minutes[2].
Night Mode Doesn't Help
The same research group tested Night Shift (Apple's night mode) vs. no phone use vs. normal phone use. All three groups fell asleep in about the same time. Night mode made no significant difference[3].
Intensity Beats Color
Research published in Current Biology found that brightness of light matters much more than its color for affecting circadian rhythms. Dim blue light affects sleep less than bright yellow light[4].
Blue Light Glasses: The Emperor's New Specs?
A 2021 Cochrane systematic review (the gold standard for evidence summaries) looked at all randomized controlled trials on blue light filtering lenses. Their conclusion?
"We found no short-term effects of wearing blue-light filtering lenses compared to non-blue-light filtering lenses on visual performance or sleep quality, and no evidence of effects on clinical measures of macular health."[5]
— Cochrane Database of Systematic Reviews, 2023That doesn't mean they're useless for everyone—some people report benefits. But the high-quality evidence for sleep improvement specifically is weak.
03 Putting It in Perspective
Here's the thing about blue light: context matters. A lot.
Your phone screen emits about 40 lux at typical viewing distance. A cloudy day outside is 10,000 lux. We're obsessing over 0.4% of the light exposure that wouldn't even make you squint outside.
04 What Actually Matters More
If blue light from screens isn't the sleep villain we've been told, what does matter about evening screen use? Turns out, quite a lot—just not what the glasses companies want you to focus on.
Content, Not Light
Scrolling through upsetting news, engaging in social media arguments, or watching intense shows activates your stress response. That's far more disruptive to sleep than the light emitted by your screen.
Mental Engagement
Your brain needs to wind down before sleep. Stimulating content—emails, games, doom-scrolling—keeps your mind active. A paper book at the same light level is less disruptive.
Time Displacement
The biggest impact of screens on sleep? They keep you up later. That "one more episode" or "quick scroll" that turns into an hour. The issue is behavioral, not photobiological.
Room Lighting
Your phone isn't the only light source. Bright overhead lights in your home expose you to far more light than your screen. Dimming room lights matters more than screen filters.
"Telling people to stop using screens before bed often misses the point. It's usually not the light— it's what they're doing on the screens."
— Dr. Michael Gradisar, Sleep Researcher
05 Practical Advice (Based on Evidence)
Given what we actually know, here's what I'd recommend:
Do This
- Dim your room lights 1-2 hours before bed—this has more impact than screen filters
- Use night mode if you like it, but don't expect miracles
- Choose calming content in the evening—what you watch matters more than the light
- Set a "devices down" time to avoid time displacement (the real sleep thief)
- Get bright light in the morning—this affects your rhythm more than evening light
- Keep screen brightness moderate—dimmer screens mean less light exposure of any color
Skip This
- Don't buy expensive blue blockers expecting transformed sleep—evidence doesn't support it
- Don't obsess over screen color while ignoring content and room lighting
- Don't think night mode = free pass to scroll until midnight
- Don't ignore the actual research because marketing sounds more convincing
If You Still Want Blue Blockers
Look, I'm not going to tell you they're worthless. If you feel they help, the placebo effect is real and valuable. And there may be individual variation the studies haven't captured.
But if you're going to buy them:
- Don't pay premium prices—cheap ones filter blue light as well as expensive ones
- Manage expectations—they're not a sleep cure
- Focus on the other factors first—they matter more
The Bottom Line
Blue light from screens has been massively overhyped as a sleep disruptor. The research shows modest effects at best—nowhere near what the $2 billion blue light products industry would have you believe.
Your screen isn't innocent—but it's probably hurting your sleep because of what you're doing on it, how long you're using it, and the bright room you're using it in. Not because of a few photons of blue light.
Save your money on fancy glasses. Dim your room lights. Choose boring content before bed. Set a screen curfew you'll actually follow. These unsexy solutions will help more than any gadget marketed with scary-sounding science.
Sources & Further Reading
- "High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light." Journal of Clinical Endocrinology & Metabolism, 88(9), 4502-4505. (2003) PubMed →
- "Effects of blue light versus white light exposure on melatonin." Chronobiology International, 36(7), 1078-1084. (2019) PubMed →
- "Losing sleep by staying connected: Night Mode may not mitigate the effects of screens on sleep." Sleep Health, 7(1), 31-36. (2021) PubMed →
- "Cones Support Alignment to an Inconsistent World by Suppressing Mouse Circadian Responses to the Blue Colors Associated with Twilight." Current Biology, 29(24), 4260-4267. (2019) PubMed →
- "Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults." Cochrane Database of Systematic Reviews, 8(8), CD013244. (2023) PubMed →
Recommended Resources
- Why We Sleep by Matthew Walker, PhD (Chapter on light and sleep)
- Huberman Lab: "Using Light to Optimize Health"
- Sleep Foundation: Light and Sleep
