Seeing the light is a choice, not seeing the light is no choice.
The pandemic has changed the working habits of millions of people around the globe. For many, remote work has quickly turned from an emergency solution to the new status quo, with many companies offering their employees much more permanent flexibility when it comes to the question of the workplace.
Getting up in the morning and facing a long and potentially traffic-jammed drive or a walk through cold and rain makes it tempting to just stay at home, to remain in the cozy confines of your bed for a little longer, and then sit down at the desk straight away.
But as much as we all appreciate the ancient technology of having a roof over our heads, this roof is tremendously effective at blocking out light, light that science shows our brains desperately need every morning. And while we have invented a lot of artificial ways of illuminating the world, there is nothing quite like the sun shining into our eyes.
Our brains need light to figure out what time it is, and our brains need to figure out what time it is to set our biological clocks. We are creatures of rhythm, of routine. We are born into a world of light and darkness, of waking and sleeping, and our bodies have two widely different modes of being: activity during the day, rest during the night.
Our bodies are composed of hundreds of independent parts that need to cooperate effectively, so nature has come up with some clever ways to synchronize all the operations going on within us, to tell our liver and our kidney and our muscles when it is time to work and when it is time to rest. In the body, a crucial part of this synchrony is achieved through a hormone called melatonin. The primary function of melatonin is to adjust our body to the cycle of day and night, also known as the circadian rhythm.
There is only one way for your endocrine system (the system that uses hormones as its messengers) to figure out what time it is: your eyes, and more specifically, the retinal ganglion cells in your eyes, need to see a certain amount of light in the early morning hours. This pulse of light early in the day tells your body it is time to wake up, triggering a cortisol spike, and setting the clock for melatonin release 16 hours later. While cortisol is well known as a stress hormone, receiving this cortisol spike during the right time of the day helps you be more alert when you need to be, boosts important functions such as your immune system, and helps you be less stressed when you don’t want to be.
The retinal ganglion cells, however, are not easily impressed, and the light shining into your eyes at these early morning hours needs to have a certain intensity. With all the nuclear fusion going on in the sun at millions of degrees, it is much brighter than your average lamp, and a lot brighter even than all your lamps and phone screens and TVs turned on at the same time.
As our biology has evolved for a couple of billion years with the sun as its primary light source, we depend on it to imprint into our brain the fact that a new day has arrived, and this “new day”-signal needs to get into your brain in the early morning hours. As a rule of thumb, you should not delay it for more than 2 hours after you get up.
A light intensity of around 10.000 Lux (the SI unit in which light intensity is measured), something you can expect during an average cloudy morning, is what you should be aiming for, and this light signal needs to last around 10–20 minutes. If it’s really sunny, 2–5 minutes might already suffice.
But for artificial light sources, it’s very hard to reach the necessary intensity to give your brain a clear signal. An artificial light source like a lamp only has an intensity in the low-hundred Lux range. Seeing the light only through a small window next to your desk likewise significantly decreases its intensity. If you are not convinced, go outside and look at the sky even during a cloudy morning. You might be surprised at how bright it really is.
There are also some apps that measure the intensity of light sources, which help you gain some intuition for these numbers. Again, there is an enormous difference between a lamp or a laptop screen and being outside, and one that makes a big difference when our brains are trying to figure out what time it is.
Many mental health issues such as depression are characterized, among other things, by a delayed cortisol spike in the evening hours, and irregular and disrupted sleeping patterns. Healthy sleep means regular sleep, and properly adjusted biological rhythms are a cornerstone for a healthy and happy life.
While lockdowns and remote work have made it much easier to stay inside all day, it is crucial for all of us to leave the house and see bright light every morning, even if only for 10 or 20 minutes, to get our rhythms going and our hormones properly flowing. It is one of the most effortless ways of optimizing sleep, being more alert during the day, and defending against all sorts of mental and physical health issues.
This article was written to raise awareness for a biological fact which I think is incredibly simple but unfortunately much less well known than it should be. For more details, Andrew Huberman’s brilliant podcast episode on sleep goes into all of this in more depth, explains the mechanisms in detail, and cites the relevant scientific sources.