Can Light Help Sleep

Sleep quality can be affected by many factors, light is definitely the most important one. While it is most people’s belief and even seems a truth that it’s easier to sleep when it’s dark, the link between light and sleep is more complex than it looks. One of the proofs is that light can largely affect circadian rhythm and melatonin, the two key factors deciding your sleep quality.

1. How Light Affects Circadian Rhythm and Melatonin

Circadian rhythm

Circadian rhythm is an internal body clock that signals when to be alert and when to rest in accordance with sunlight and darkness. It coordinates a wide range of processes in the body, including sleep. This rhythm is controlled by a small part of the brain, known as the circadian pacemaker, that is powerfully influenced by light exposure.

The timing of light exposure is a major way light changes circadian rhythm. The earlier you perceive light in the morning, the earlier your sleep schedule will be. Likewise, light exposure in the late evening will push the sleep cycle and delay bedtime.

Both excess or poorly timed artificial light exposure causes your circadian rhythm misaligned with the day-night schedule. This can throw your sleep out-of-whack and induce other health impacts including cognitive impairment, metabolic syndrome, and psychiatric illness including depression.


Melatonin is an essential sleep-promoting hormone that is naturally produced by the body based on its judgment of light environment. In response to darkness, the pineal gland in the brain initiates the production of melatonin, but light exposure slows or halts that production.

When melatonin levels rise, it’s easier for people to fall asleep. In addition, daily cycles of melatonin production normalize circadian rhythm, reinforcing a stable sleep-wake schedule.

For some people with sleeping problems, including circadian rhythm disorders, synthetic melatonin, available as a dietary supplement, may be prescribed to help regulate sleep timing.

Negative impacts of artificial light

When exposed to only natural light, both circadian rhythm and melatonin production are closely synchronized with sunrise and sunset, making people awake during the day and asleep when it’s dark. Yet with ubiquitous electricity in modern society, you are now constantly living with artificial light. Therefore, the two key factors to sleep are 24/7 negatively affected and sleep quality is inevitably damaged.

2. How Light Helps Sleep

While artificial light is exerting so negative impact on circadian rhythm and melatonin, the good thing is that knowing the complex links between light and sleep possibly allows you to scientifically and correctly utilize light to gain consistent, high-quality sleep.

How light helps sleep at day

Light therapy has been accepted and trusted by quite many people in that it can treat some people with insomnia and circadian rhythm sleep disorders by letting them sit in front of devices like lighting boxes for some time each day. There is science behind this. When sitting before light, your eyes’ retinal cells perceive the light from the light therapy box, affecting certain chemicals in your brain. These chemicals are melatonin and serotonin, and they’re responsible for regulating your sleep-wake cycle. The perception of light constrains the production of your brain’s melatonin, keeping you awake and energetic. It’s especially effective for those who have “phase-delayed” circadian rhythm, which means a person’s circadian rhythm is relatively behind a normal one so he starts to sleep and wake up at later times.

But light therapy boxes are not limited. They can be tablet-like devices, floor lamps, desk lamps, table lamps, alarm clocks and many other devices. Taking desk lamps as an example, they are so welcomed by workers who have no time for treatment at day. By lighting up the lamp on the desk. They can receive treatment while working.

How light helps sleep at night

When it comes to sleep at night, your ability to sleep could be determined by different wavelengths of light. This is because evolution has hardwired our bodies to respond to the full spectrum of light provided by the sun, in various ways. Blue wavelengths of light, similar with sunlight, are highly stimulating to photoreceptors; red wavelengths of light, not so much. 

Blue light, as part of the normal spectrum of sunlight during the day, acts as a beneficial stimulant, boosting alertness, mood, attention, and reaction times. But that’s not suitable for sleep. Research into the adverse effects of blue light, such as that emitted by computers, smartphones, and energy-efficient lighting, shows a direct correlation between nighttime blue light exposure and sleep disorders. Even low levels of blue light suppress production of melatonin.

Red light, with its low color temperature and conducive wavelength for a sound sleep, has been proved by more researchers that it could help soothe and relax people and stimulate melatonin production to help people fall asleep more naturally.

That’s why it is widely believed that blue light prevent you from sleeping while red light can help produce melatonin and contribute to sleep.

Personal preference

The impact of light on sleep depends on not only the wavelength as analyzed above but also personal preference to light colors. That seems novel to most people, but a 2017 study found strong evidence for it. In this study, researchers ran different experiments and found that those who were exposed to their preferred light colors fell asleep quicker, proving individual taste of colors could also play a role in determining which color light is best for inducing sleep. 

In this aspect, a lighting device that can offer multi-colors to meet various individual tastes is seemingly a effective solution to sleep problem.

3. Conclusion

Since the world is now illuminated by artificial light anytime, modern human’s circadian rhythm and melatonin production cannot be as natural as hundreds of years ago. Given this crucial fact, corresponding measures must be taken to minimize their negative impact on sleep. Out of question, among all the existing treatments, some may be related to medicine and psychology, but systematically using light to correct the circadian rhythm and melatonin production can always play a role in benefiting your sleep.