Why We Sleep Better in a Dark Room
If you've ever been cheered by a sunny day or felt gloomy on a cloudy one, it will probably come as no surprise that light has a powerful effect on our sleep cycle, mood, and overall well-being.
Scientists have long studied the role that light, both natural and artificial, plays in regulating our biological clock, circadian rhythm, hormones, body temperature, and more. And every year we learn more about the ways exposure to light impacts not only our physical health but also our mental health and the way we behave.
The connection between sleep and light
The Industrial Revolution marked the beginning of society's increased exposure to light and, as modern society has progressed, our light sources have become even more varied and around-the-clock.
"The increasing rate of depressive disorders in humans corresponds with the increasing use of light at night in modern society," says Randy Nelson,1 a professor of neuroscience at West Virginia University who conducted a leading study on the matter. "Many people are now exposed to unnatural light cycles, and that may have real consequences for our health."
Numerous studies2 have linked exposure to light at night with depressive disorders. With electronics and social media usage soaring over the past two decades, blue light3, in particular, has become notorious for its deleterious effect on our mental health. Though blue light is naturally emitted from the sun, persistent exposure to it at night via our electronic screens inhibits the production of melatonin. This in turn affects our circadian rhythm and the quality and quantity of sleep we get.
Even artificial outdoor light from streetlights, for example, can have a big impact on our sleep. A new study4 from the National Institute of Mental Health found that teens who live in areas that have high levels of artificial light at night tend to get less sleep and are more likely to have a mood disorder. (Learn more about the differences in sleep quality between people who live in the country versus those who live in the city here.)
What you can do
Too much light at bedtime and people tend to have difficulty falling asleep. Too little of it during the day, and the same problem may occur. So how do you strike the right balance to maximize your chance of deeply restorative sleep?
Here are some tips from sleep experts and neurologists:
- Make your bedroom as dark as possible: The National Sleep Foundation recommends5 keeping your bedroom dark with the help of blackout curtains or an eye mask. And if you do wake during the night to use the restroom, resist the urge to turn on a light, using only a low-illumination nightlight if possible.
- Turn off the screens: The blue wavelengths emitted from our phones, tablets, televisions and computer screens suppress the melatonin that tells our bodies it's time for sleep, according to research conducted at Harvard.6 Sleep scientists suggest avoiding screens for two to three hours before bed—or, if that's not possible, wearing blue-blocking glasses at night to filter out that wavelength.
- Tech for better sleep: Not all technology gets in the way of a good night's sleep. There are all kinds of tech gadgets on the market that will help you get your light exposure just right. Lighted alarm clocks or sunrise alarm clocks that mimic daybreak are designed to rouse you without the adrenaline rush associated with a jarring noise. And during the day, exposure to light can be therapeutic for insomnia sufferers, hence the prevalence these days of light therapy7 in the form of light boxes and light visors.
- "Too Much Light at Night May Cause Depression," SleepFoundation.org, July 2020.
- "Timing of light exposure affects mood and brain circuits," Translational Psychiatry, January 2017.
- "How Blue Light Affects Mental Health," by Christine Dearmont, Mental Health America.
- "Outdoor light linked with teens' sleep and mental health," National Institutes of Health, July 2020.
- "Lights Out for a Good Night's Sleep," SleepFoundation.org., updated July 2020.
- "Blue light has a dark side," Harvard Health Letter, May 2012.
- "Light Therapy for Insomnia Sufferers," SleepFoundation.org, updated July 2020.