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Sleep and Light Exposure

Sleep and LightThe information and research findings on sleep are coming fast and furious these days. There seems to be a backlash to the cult of productivity and the former “badge of honor” for functioning on the least amount of sleep. There is a recurrent theme, which is that by not making restorative sleep a priority, there are both short-term and longer term negative consequences.

The negative impact of too much artificial light has become increasingly more relevant, as many of us are using multiple light-emitting devices right up until when our head hits the pillow. If you are interested in the optimal functioning of the human organism, it’s time to evaluate your sleep quantity, quality, and routine, as well as your exposure to both natural and artificial light.

Observe and track your pattern of light exposure during the day and after dusk. When considering back-to-basics sleep for humans, I often think about what life was like before the advent of electric light. Humans rose with the sun and retired when the sun went down. They did not spend most of the day indoors with fluorescent light and did not have light stimulation after sundown. Their daytime light exposure was to natural light only, which is much more powerful than modern indoor lighting. Modern technology has given us the power to manipulate the environment to the point where the sun potentially never sets.

Artificial light after dusk interferes with the production of the hormone melatonin, which regulates the sleep cycle, and disrupts the circadian rhythms. Circadian rhythms include physiological, cognitive, and behavioral changes that follow an approximately 24-hour cycle, responding mainly to light and darkness in the outside world.

Light is the single most important external factor that influences circadian rhythms. Modern humans living in industrialized societies typically do not get enough light during the daytime hours, and then get too much artificial light in the evening. By limiting your artificial light exposure in the hours before bed, you could assist your body in preparing naturally for restful sleep.

Try to get out into the light during the daytime, even if it is only for 15 minutes. Experiment with minimizing artificial light the closer that you get to bedtime. Ideally, one hour before bed, you would only have exposure to very dim light.

Try not to use any electronic devices or watch television during that one hour. Reading a print book or magazine may be a better option than an electronic one. Notice if this simple change in routine enhances your ability to fall and stay asleep.

If an hour is unrealistic based on your lifestyle, you may consider installing software to adjust the light level to reduce the stimulating effects. If you are using electronic devices in the evening, you may want to consider installing f.lux, which adapts the light emissions from your computer to the time of day. It changes to sunlight during the day, and warm at night, drastically reducing the blue light emitted. Blue light is the most disruptive to melatonin production and circadian rhythms.

You can access the program at The website has more interesting information and lists numerous research references. I have noticed a drastic difference in my ability to fall asleep on nights that I am using my laptop after installing f.lux. A jailbreak is required for download on other devices, and the generous creators are working on alternatives for users for whom the break is not a viable option.

Getting natural light during the day can be a challenge, especially in the winter. After researching options for addressing daytime light deficiency, I purchased a blue light therapy device (I purchased the Philips goLITEBLU, but there are multiple available purchase options), that I keep by my computer at work during the day. I have experimented with different dosages, and found that for me personally, 20 minutes in the mid-morning and 20 minutes in the early afternoon seems to be effective on days that I cannot clock sufficient natural bright light exposure.

Another area to be attentive to is the darkness of your bedroom. Darker is better. Clocks and devices that emit blue light suppress melatonin production. Red and amber light are the least disruptive to circadian rhythms.

Keep the room dark by keeping your electronic devices switched off, and use black-out shades or a sleep mask as needed. Don’t check email or clock watch if you wake during the night. If any devices or clocks need to be left on, remember that dim red light displays are the least disruptive.

If you have significant and consistent sleep difficulties, a medical evaluation with a sleep specialist may be warranted, depending on individual circumstances. The National Sleep Foundation offers a directory of providers at

Controlling light exposure and adequate length and quality of sleep are absolutely essential elements to creating resilience and the ability to function optimally in all areas of life. So while preparing for winter, don’t forget to include both light exposure and adequate amount of sleep as part of your overall plan.


Centers for Disease Control and Prevention (2011). Effect of short sleep duration on daily activities — United States, 2005-2008. MMWR. Morbidity and Mortality Weekly Report, 60(8), 239.

Matthews, M., Carroll, E., Abdullah, S., Snyder, J., Kay, M., Choudhury T. & Kientz, J. (2014, April). Biological rhythms and technology. In CHI’14 Extended Abstracts on Human Factors in Computing Systems (pp. 123-126). ACM.

Mercola, J. M. (2014). How the Cycles of Light and Darkness Affect Your Health and Wellbeing. website, accessed April 14, 2014.

Sleep and Light Exposure

Frances L. Hennessey, LICSW

Frances L. Hennessey, LICSW is a social worker, psychotherapist, and registered yoga teacher. She currently works with active duty military and their families.

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APA Reference
Hennessey, F. (2018). Sleep and Light Exposure. Psych Central. Retrieved on November 29, 2020, from
Scientifically Reviewed
Last updated: 8 Jul 2018 (Originally: 28 Sep 2014)
Last reviewed: By a member of our scientific advisory board on 8 Jul 2018
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