The Blue Light Myth: Why Scientists Are Rethinking Everything We Know About Screens And Sleep

The sentiment is so often-repeated that it feels like common sense: the blue light from your phone tricks your brain into staying awake when you should be sleeping, and is more likely to suppress sleep hormone melatonin than, e.g., yellow light.

For that reason, some phones have a “night mode” which turns the colour of your screen warmer in the hours before your bedtime. Many sleep experts advise steering clear of screens at night altogether.

But this finding isn’t as consistent as you might think. The BBC recently published a report suggesting that it “isn’t ruining your sleep” at all. 

The research around blue light is mixed 

Yes, there are lots of papers which have found that blue light at night can mess up your Circadian rhythm, thus negatively impacting your sleep.

However, others found different results.

A 2023 study from the University of Basel in Switzerland and the Max Planck Institute for Biological Cybernetics in Germany exposed participants to three light conditions, including blue and yellow light, an hour and a half after their bedtimes. 

All light forms seemed to negatively affect sleep. But the scientists found “no conclusive evidence” that blue light was any worse than others.

Other research has found that blue light from our screens probably doesn’t affect our melatonin levels as much as we might expect.

A systematic review published in Frontiers in Physiology reads, “in general, the specific effects of blue light exposure seem still to be a murky field and more investigations are needed before final firm and evidence-based conclusions can be drawn”.

And a review of studies involving blue-light blocking lenses found mixed results, noting that often, researchers didn’t compare the effect of blue light to that of other light on people’s sleep, even though “exposure to even moderate light levels, in addition to short-wavelength light, can acutely suppress melatonin”. 

Does that mean screens before bed are A-OK? 

There’s more to consider here than just blue light. Some screen activities, like games, may excite more activity in the brain than others. 

Still, Dr Michael Gradisar, head of sleep science at Sleep Cycle, said that “We published a review of scientific investigations into the links between screens and sleep, and the data do not support the recommendation that people avoid screens in the hour before bed.” 

Instead of avoiding them entirely, he added, it might be “more effective to encourage individuals to try less engaging, less disruptive devices before bed as a practical path to better sleep,” like TV. 

Additionally, while researchers don’t agree on whether blue light is uniquely bad for us, any artificial light at night has the potential to mess with our body clock.

We do know that morning sunlight is especially good at keeping our internal rhythms on track, and that “zeitgebers,” or time markers like meals and exercise, can help too.

But if you’re happy with your sleep despite your nighttime scrolling, not everyone is convinced there’s enough evidence to give up the habit entirely.