The pandemic saw a veritable explosion in the use of electronics. Remote work aside, lockdowns combined with fear and anxiety over COVID-19 caused many people to escape into the digital world, particularly through social media. However, while certain aspects of our lives have returned to normal, the average time spent using electronics has not, with adult use alone increasing by 60-80%.¹
The effects of excessive screen time on our health are concerning, especially considering the role light plays in regulating circadian rhythms. A healthy cycle of sleep and wakefulness keeps our body functioning at its best. Blue light from screens disrupts these cycles and, if not corrected, can lead to obesity, depression, sleep disorders, and other health conditions.²
Before diving into blue light and its impacts on our health, it’s important to understand how our body’s internal patterns, called circadian rhythms, are maintained. Every organ and tissue in your body has a biological clock comprised of specific hormones and neurotransmitters that help to regulate these patterns.² Circadian rhythms run on a 24-hour cycle and are responsible for many of our body’s functions, including:³
These essential biological functions are kept in sync by the body’s master clock, the suprachiasmatic nucleus (SCN).¹⁵ The SCN is a structure comprising about 20,000 neurons in the brain’s hypothalamus that directly responds to changes in visible light in the environment.
At night, or when our eyes detect less light, the SCN tells the brain to produce more melatonin, the hormone that makes you sleepy.¹⁵ Because the SCN receives its information directly from your eyes, its response can get thrown off by various factors, including, but not limited to, changes in your schedule, traveling to different time zones, working night shifts, and blue light from electronics.²
There’s an entire spectrum of colors and types of light, but blue light may impact our bodies and brains the most.⁶ The largest source of blue light is the sun, meaning that when the SCN responds to day and night, it’s actually responding to changes in blue light.⁴ The light emitted from the sun, including blue light, is particularly beneficial; it lifts our spirits, makes us more alert, and naturally regulates our circadian rhythms.⁵ Research has shown that natural sunlight can even reduce the risk of children developing myopia, also known as nearsightedness.¹⁶
While natural sources of blue light can be beneficial, artificial ones that go against your body's cyclical rhythms can be detrimental to your health. Blue light has the most energy per photon, or particle, and can be harmful if looked at too closely or for too long. Electronic devices such as smartphones, tablets, and laptops are the largest producers of artificial blue light, particularly those with LED backlit screens. Excessive use of these devices, especially at night, can confuse the SCN, cause disruptions in our circadian rhythms, and ultimately affect our sleep quality.⁴
As mentioned before, the brain's master clock (the SCN) responds to changes in visible light. When we use electronics at night, the blue light from these devices causes the SCN to suppress melatonin production. An experiment conducted by Harvard found that 6.5 hours of blue light exposure led to melatonin suppression lasting 3 hours.⁶ Inadequate sleep, decreased melatonin levels, and chronic disruptions in circadian rhythms have been linked to the development of the following health concerns:⁶ ⁷
Children and teens, whose eyes and brains are still developing, are most at risk for developing cognitive and neurological issues due to excessive screen time.⁸ A lack of sleep and disruptions in the circadian rhythms of younger people can lead to issues with academic performance, emotional regulation, and obesity.⁹
The American Academy of Pediatrics (AAP) recommends that children younger than two have no screen time at all, with guidelines for older children and teens suggesting no more than 1-2 hours per day.⁹ It can be difficult for parents to reduce screen time for children and teens, as at least 65% of students use the Internet to complete homework assignments.¹⁸ Even if you can’t reduce your child’s screen time during the day, some pediatricians recommend limiting blue light-emitting electronics before bed.¹⁰
It can be tough to stop scrolling through social media before bed, but excessive use of electronics at night can also cause eye problems. The most commonly reported condition is eye fatigue, which includes the following symptoms:¹¹
A common concern heard by retinal specialists is worry about blue light from electronic devices causing damage to the eyes.⁴ It’s important to note that the research surrounding potential retinal damage from blue light is conflicting. Some animal studies suggest chronic exposure to blue light from electronics can cause various forms of retinal damage.¹² Eye doctors, on the other hand, say there isn’t enough conclusive evidence to validate the claim that blue light affects retinal or ocular health.⁴ ¹⁷
The simplest way to reduce blue light exposure at night is to avoid bright screens and blue light-emitting devices 2-3 hours before bed.⁶ While ideal and effective, it may not be the most realistic solution for some. Thankfully, there are other options, though not all have been proven as effective as reducing screentime:
Installing a blue light filter app on your devices can reduce your exposure. These apps block the blue light wavelength by adding an amber or yellow tint to your screen. Many filter apps include a timer to turn on automatically in the evening.⁶
Wearing blue-light-blocking glasses is an option, but research has been inconsistent on their effectiveness.¹³ One study found that wearing amber-colored blue-light-blocking lenses improved outcomes in patients with insomnia. These lenses absorbed 65% of blue light while allowing green and red light to pass. The patients wore the lenses for two hours before bed and experienced improved sleep quality and duration.¹⁴ If you decide to use blue light-blocking lenses, we recommend first speaking to an ophthalmologist about your situation and following their recommendations.
Using a red night light can help reduce your blue light exposure and its side effects. Red light is not as likely to interrupt circadian rhythms or suppress melatonin production, and it may even be beneficial to your sleep.⁶ A small study conducted in 2012 showed that red light improved the quality of sleep, serum melatonin levels, and endurance of 10 female athletes.¹⁹
It can be challenging to balance our digital and physical lives in today's fast-paced world. However, it’s important to remember that too much blue light exposure from screen time can affect your circadian rhythms and has been linked to various health problems, such as depression and diabetes.² Sleep disruptions and mood changes may be warning signs that you should reassess your screen time habits. If you’re experiencing difficulty falling asleep or staying asleep, it might be helpful to consider limiting your electronics use 2-3 hours before bedtime.⁶ If your symptoms persist, a health professional could offer additional guidance.
 Pandya, A., & Lodha, P. (2021). Social Connectedness, Excessive Screen Time During COVID-19 and Mental Health: A Review of Current Evidence. Frontiers in Human Dynamics, 3. Retrieved February 17, 2023, from https://www.frontiersin.org/articles/10.3389/fhumd.2021.684137/full.
 National Institutes of Health. (2019). Circadian Rhythms. NIH. Retrieved February 17, 2023, from https://nigms.nih.gov/education/fact-sheets/Pages/Circadian-Rhythms.aspx.
 MD, L. E. (2020, May 13). Why your sleep and wake cycles affect your mood. Harvard Health Blog. Retrieved February 17, 2023, from https://www.health.harvard.edu/blog/why-your-sleep-and-wake-cycles-affect-your-mood-2020051319792.
 Ramsey, D. (2019, May). Will blue light from electronic devices increase my risk of macular degeneration and blindness?. Harvard Health Blog. Retrieved February 17, 2023, from https://www.health.harvard.edu/blog/will-blue-light-from-electronic-devices-increase-my-risk-of-macular-degeneration-and-blindness-2019040816365.
 Health, C. (2022, August 3). How blue light affects your eyes, sleep, and health. Cultivating-Health. Retrieved February 17, 2023, from https://health.ucdavis.edu/blog/cultivating-health/blue-light-effects-on-your-eyes-sleep-and-health/2022/08.
 Harvard Health Publishing. (2020, August 13). Blue light has a dark side. Harvard Health. Retrieved February 17, 2023, from https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side
 Wahl, S., Engelhardt, M., Schaupp, P., Lappe, C., & Ivanov, I. V. (2019). The inner clock—Blue light sets the human rhythm. Journal of Biophotonics, 12(12). Retrieved February 17, 2023, from https://onlinelibrary.wiley.com/doi/10.1002/jbio.201900102.
 Manwell, L. A., Tadros, M., Ciccarelli, T. M., & Eikelboom, R. (2022). Digital dementia in the internet generation: excessive screen time during brain development will increase the risk of Alzheimer's disease and related dementias in adulthood. Journal of integrative neuroscience, 21(1), 28. Retrieved February 17, 2023, from https://www.imrpress.com/journal/JIN/21/1/10.31083/j.jin2101028.
 Christensen. (2021, May 28). Children and screen time: How much is too much?. Mayo Clinic Health System. Retrieved September 21, 2022, from https://www.mayoclinichealthsystem.org/hometown-health/speaking-of-health/children-and-screen-time
 Ruder, D. B. (2019, June 19). Screen Time and the Brain. Harvard Medical School. Retrieved February 17, 2023, from https://hms.harvard.edu/news/screen-time-brain
 Hartl, D. K. (2021, July 8). Is Too Much Screen Time Giving You Eye Fatigue?. Harvard Business Review. Retrieved February 17, 2023, from https://hbr.org/2021/07/is-too-much-screen-time-giving-you-eye-fatigue
 Research progress about the effect and prevention of blue light on eyes. (2018, December 18). International Journal of Ophthalmology. Retrieved February 17, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288536/.
 Vagge, A., Ferro Desideri, L., Del Noce, C., Di Mola, I., Sindaco, D., & Traverso, C. E. (2021). Blue light filtering ophthalmic lenses: A systematic review. Seminars in ophthalmology, 36(7), 541–548. Retrieved February 17, 2023, from https://www.tandfonline.com/doi/full/10.1080/08820538.2021.1900283.
 Shechter, A., Kim, E. W., St-Onge, P., & Westwood, A. J. (2018). Blocking nocturnal blue light for insomnia: A randomized controlled trial. Journal of psychiatric research, 96, 196. Retrieved February 17, 2023, from https://www.sciencedirect.com/science/article/abs/pii/S0022395617308592?via%3Dihub.
 Ma, M., & Morrison, E. (2022). Neuroanatomy, Nucleus Suprachiasmatic. StatPearls Publishing. Retrieved February 17, 2023, from https://www.ncbi.nlm.nih.gov/books/NBK546664/.
 Trautner, T. (2016, October 7). The benefit of daylight for our eyesight. Michigan State University. Retrieved February 17, 2023, from https://www.canr.msu.edu/news/the_benefit_of_daylight_for_our_eyesight.
 American Optometric Association. (2019, July 11). Blue-light hype or much ado about nothing?. AOA. Retrieved February 17, 2023, from https://www.aoa.org/news/clinical-eye-care/health-and-wellness/blue-light-hype-or-much-ado-about-nothing.
 Browning, J. (2021, March 22). Broadband as a Utility Is a Matter of Ethics, Not Economy. Ethical Tech - Duke University. Retrieved February 18, 2023, from https://ethicaltech.duke.edu/2021/03/22/broadband-as-a-utility-is-a-matter-of-ethics-not-economy/.
 Zhao, J., Tian, Y., Nie, J., Xu, J., & Liu, D. (2012, November 1). Red Light and the Sleep Quality and Endurance Performance of Chinese Female Basketball Players. Journal of Athletic Training, 47(6), 673-678. Retrieved February 18, 2023, from https://meridian.allenpress.com/jat/article/47/6/673/111318/Red-Light-and-the-Sleep-Quality-and-Endurance.