#161 - Melatonin Suppression: Look Below The Surface
It’s Day One of 2025 - but the message from 2024 hasn’t changed … much.
My new motto for 2025 is a new Aussie saying, which I’ll paraphrase … “Well, I’m not here to fuck spiders.”
In 2025 I plan to go deeper into scientific studies; to provide more underlying details. Even lateral details.
On reflection, the biggest career highlight of 2024 for me was our peer-reviewed publication of technology use and sleep (peer-reviewed means scientific experts vetted the manuscript and there was a consensus that it was of sufficient scientific quality to be published in a scientific journal).
For almost a decade - since we published the world’s first test of altering blue-enriched screen light on sleep - I’ve been trying to turn the tide of misinformation. To correct the statement that viewing the blue-enriched screenlight before bed makes it difficult to fall asleep.
When we started planning and writing this paper in 2023, we knew we had to show readers ‘Table 1’ - which would be the data itself, collated from all the studies that had tested blue-enriched screenlight on the time taken to fall asleep (sleep onset latency). We knew people wouldn’t go and search for these data. So we made the job easier and brought it to them.
On reflection, I am sincerely grateful to every single reader who has been open to learning about these ‘new’ data. That they are open to evolving their thinking.
On reflection, I am also perplexed at the range of experts who are highly resistant to ‘new’ data. - even when they have no data to support their opposite view.
To this end, I plan to write more WINK articles that provide deeper details. These articles are intended for those wanting to learn; wanting to evolve.
And a lot of what I will write in 2025 will be about a remarkable hormone - Melatonin.
So first, let’s start diving deep into whether …
Blue-ENRICHED Screen LIGHT SuppressES Melatonin
On the surface, this statement appears true.
That is, if you look at all the studies that have tested whether our natural levels of melatonin get suppressed by a bright, blue-enriched screen before bed, then you’ll see almost all of them report the same consistent finding.
The finding is that there is a statistically significant suppression of evening melatonin. See the example abstracts below …
So if you stick to just reading the abstracts, you will see that time and time again, evening melatonin suppression occurs when exposed to a bright screen.
This is where a lot of experts and their copycats end - but let’s go one level deeper …
Melatonin is not “Quashed” …
Below is a figure taken from one of those studies above that reported a significant suppression of melatonin. This study compared two types of screens - an old screen that emitted less blue light (Non-LED Screen) and a more modern screen that has a higher output of blue-enriched light - like the one you’re reading this blog on (LED screen).
You can see that beautiful rise in evening melatonin when the Non-LED screen was used (White Dots). Melatonin begins rising just after 8 PM and continues to beautifully fly towards the heavens.
Taken from Cajochen and colleagues (2011), Journal of Applied Physiology
Now, take a careful look at what happens to melatonin in the face of an LED screen (Black Dots). The things you should notice are:
Melatonin still rises across the evening when an LED screen is used!
There is suppression of melatonin by an LED screen, but it’s not much. It’s actually closer to the non-LED levels than compared to zero (ie, no production of melatonin).
Across the evening there are 4 times when melatonin is statistically lower in the LED group. These are marked with asterisks (*) on the x-axis at 21:15, 22:15, 22:45 and 23:15.
If you look at say the significantly lower melatonin at 22:15 (ie, 10:15 pm), the LED group has around 3 pg/ml whereas the Non-LED group’s melatonin is around 4 pg/ml - so you could say the melatonin suppression is about 25%.
Now a 25% suppression of melatonin is worth paying attention to, given melatonin is an incredibly important hormone - as you will learn throughout 2025.
But as you’ll see from the quote below - this evening melatonin that is measured in these studies is the melatonin that is produced from the pineal gland, in the centre of our brain - which accounts for an incredibly small percentage of our body’s total melatonin count.
This means LED screens suppress 25% of the 5% of our body’s melatonin (i.e., just over 1% of our body’s naturally occurring melatonin).
But technically, this above statement isn’t true. That’s because - I believe - the ‘recipe’ in these melatonin suppression studies is not being followed in the real world. Here’s one ingredient …
PRE-SCREEN DARKNESS
Prior to being exposed to an LED screen, these studies will often place subjects into darkness, for about 30 to 60 minutes .You can see this in the melatonin suppression graphs (eg, “Dark Adaptation” in the figures below).
Essentially, the subjects are having their eyes adjusted to darkness, before being exposed to light. It sort of cleanses the body from the previous exposure to light.
This is one of the ingredients that is required for melatonin suppression to occur in response to an LED screen.
And here’s what happens when a study forgets to provide subjects with this ‘Dark Adaptation’. The figure below is from a Swedish study that exposed their subjects to continuous light prior to LED screen exposure.
Taken from Rångtell et al (2017), Sleep Medicine
This is one study that did not perform Dark Adaptation, and they did not observe significant melatonin suppression in response to using an LED screen.
Now think about how many people finish their work day, go home, eat dinner and do all those chores to end their day, and then sit in fucking darkness for at least 30 minutes before going on their LED screens?
Do you know anyone who does this?
Because I don’t - but apparently a lot of experts and their copycats seem to think most of the population do this.
And this is just one ingredient - what about another ingredient, like ….
A (WHITE) BRIGHT SCREEN
In order to get this 1-ish percent melatonin suppression, these studies need to max out the LED screen they use by doing two things:
putting the screen up to full brightness, and
having a white background.
For example, the Cajochen et al (2011) study had subjects watching a movie set in the snow, such the predominant colour displayed was white. This team’s subsequent study (van der Lely et al., 2015) also used a predominantly white background using a computer screen.
When we tested adolescents in our 2014 study with iPad 2s, we used music videos, text, and games that all had a white background - with the iPad 2 brightness set to 100%, 50 cm away from their faces.
When we measured the lux (ie, the brightness of the light received by our eyes) in our study, it maxed at 80 lux, which isn’t much, even though it felt really bright.
And immediately after this lux test I had a light bulb moment - the majority of people are not using a fully bright screen with a predominantly white background.
But wait, there’s another ingredient …
1.5 HOURS
We’ve often heard of the ‘sleep tip’ to avoid screens in the hour before bed, with some people and organisations reasoning that screens contain blue light that suppresses melatonin (which they believe makes it hard to fall asleep).
So let’s have a look at three early studies that tested the length of time one needed to be in front of a … white … maximally bright … LED screen.
We’ve already seen that the Cajochen et al. (2011) study found melatonin suppression first occurred at 21:15, which was almost a couple of hours after they began viewing the screen.
In 2013, Woods et al. used an iPad and found that melatonin suppression did not occur after the first hour of use, but it did by the second hour of use.
Then, van der Lely et al. (2015) found that melatonin suppression occurred from 1.5 hours of bright screen use … or said another way, the blue-blocking glasses prevented significant melatonin suppression after 1.5 hours of continuous use of a predominantly white, very bright screen, after 30-min of dark adaptation.
These studies provide evidence that melatonin suppression does not occur when using a bright blue-enriched LED screen in the hour before bed. However ….
TRY YOUR OWN EXPERIMENT
This suggestion is more of a ‘Call to Action’ to the experts who are resistant to delve this deep - but I guess with my experiences observing people’s behaviour change (as a clinical psychologist and a clinical researcher), it’s likely it will be the ones open to learning who will try this little experiment.
One evening this week, do this:
give your eyes a ‘reset’ - by being in darkness for 30-min (preferably early in the evening).
then grab your favourite device. Whether it’s a phone, tablet, laptop, TV or computer screen.
plan ahead and make sure you’re gonna watch a predominantly white screen. It might be a book. A music video or game.
And finally, max out the brightness on that screen.
Now, use your device for 1 hour - after all, I don’t want you to suppress even 1% of your melatonin (which is what will happen if you use it for 1.5 hours or more).
By performing your own experiment, you will had had an experience - maybe even a light bulb moment - where you realise, “Who the fuck does this?!”
Well my friend, you’ve asked the wrong question. The question should be …
WHO THE FUCK DOES THIS EVERY DAY OF THE WEEK?!
My guess - as a scientific authority on this very topic - is “Fuck all” - that’s who - and that’s my scientific answer.
As such, this means that despite the vast majority of human beings using an LED screen in the hour before bed, that they are not significantly suppressing their natural levels of melatonin because of it.
And the answer to my next question is “Fuck all” - the question is …
“How many people, even experts, will go to this level, to this depth, to understand if the LED screens that people use every night suppresses melatonin or not?”
CONCLUSIONS
As you can see, we have drilled down deep, through different layers of evidence, to challenge experts’ claim that blue screen light suppresses melatonin.
In my experience over the past decade, when people’s scientific belief is challenged, when they are pinned down, what they will do is sidestep. So here’s some examples of what an expert’s retort will be to this article:
“This is so narrow. You haven’t said anything about delaying the circadian rhythm of melatonin, which ‘we know’ happens in response to 480nm light” - Yep, I have drilled deep into one concept. But be patient. In 2025, you’re not just gonna hear about the misunderstanding of melatonin suppression, but also melatonin ‘delay’.
“OK, but there’s so much more to technology than just the light. ‘We know’ that these devices are engaging. That technology companies are trying their best to keep people hooked and continuously using their devices. And the content is stimulating making it harder to fall asleep. You’ve said nothing about these things.” - To use a metaphor, have you ever seen someone dig a hole in the summer heat, only to have some bystander come along and say “So how come you didn’t dig a trench?”. Well, here’s the trench we dug last year.
“You’re focusing way too much on screens. A lot of people have house lights on. ‘We know’ from studies that modern lighting has blue-enriched lighting that suppresses melatonin”.
So much of this statement is true, albeit it’s a little surface-y (ie, doesn’t go deep enough). But regardless, it’s a pathetic counter-argument as it does not negate any of the arguments I’ve outlined above. If an expert wishes to say this house lighting, it should be prefaced by an agreement that it’s highly unlikely that the world is experiencing melatonin suppression due to LED screens. And if that agreement occurs, then maybe we will see that experts can evolve their thinking …Prof MG