Studies: Health Effects of Blue Light Exposure

In August 2018, the Harvard Health Letter, a news website maintained by Harvard Medical School, published an article entitled “Blue Light Has A Dark Side.” It explained that exposure to blue light at night affects the quality of sleep of involved individuals because it suppresses the natural secretion of melatonin. Disrupted sleep has been linked to numerous health problems.

Note that melatonin is a hormone released primarily by the pineal gland that regulates the sleep-wake cycle. Melatonin supplements have also been marketed as a short-term treatment for individuals having trouble sleeping due to jet lag or shift work. Nevertheless, a disturbance in the natural secretion of this hormone leads to a disrupted circadian rhythm or biological clock.

It is also worth mentioning that there are different sources of blue light. Most notable ones are the twisted nematic or in-plane switching LCD and OLED display panels of smartphones, tablet computers, and laptops. Other prominent sources are fluorescent lamps and LED lamps, especially the white variants of these lamps that actually produce visible light within the blue spectrum. Natural sunlight has a relatively high spectral density of blue light, thus making exposure to such not a new or unique phenomenon.

Explaining the Purported Negative Health Effects of Blue Light Exposure

The Harvard Health Letter referenced two studies to explain how blue light affects individuals. One study conducted by Harvard researchers and their colleagues revealed that blue light exposure suppressed melatonin about twice as long and shifted the circadian rhythms by twice as much than exposure to green light.

Another study by researchers from the University of Toronto involved comparing the melatonin levels of two groups of people: one exposed to bright indoor light while wearing goggles that blocked blue light and the other one exposed to regularly dimmed light without wearing goggles. Findings revealed similar melatonin levels between the two groups.

The study of A. M. Chang, D. Aeschbach, J. F. Duffy, and C. A. Czeisler revealed that people who read on devices took longer to fall asleep, had less REM sleep, and had higher alertness level before bedtime than those who read in printed books. Furthermore, those who read on devices took longer to wake up and were sleepier.

Blue light exposure can also damage the eyes according to other studies. A review by G. Tosini, I. Ferguson, and K. Tsubota noted that such exposure, particularly coming from LED lamps, could induce photoreceptor damage. However, it suggested the use of LED lamps with an emission peak of around 470 to 480 nm.

The study of K. Ratnayake, J. L. Payton, O. H. Lakmal, and A. Karunarathne examines the link between blue light exposure and macular degeneration. In a laboratory experiment, they found out that the light causes a type of molecule called retinal to trigger reactions that generate poisonous chemical molecules in photoreceptor cells, thus destroying these cells in a similar way to age-related macular degeneration.

What makes this specific light damaging than the other colors in the visible light is that it rests at the end of the spectrum—just before the ultraviolet range of the entire electromagnetic spectrum. Compared to red or green light, blue light has more energy per photon, thus making it more likely to cause damage when absorbed by various cells in the body.

Arguments Against the Supposed Negative Health Effects of Blue Light

Writing as a contributor for the Harvard Health Blog, David Ramey, a specialist in retinal disease and surgery, noted that high-intensity blue light from any source is potentially damaging to the eyes. However, the levels of light emitted from consumer electronic devices such as smartphones are negligible, especially in terms of increased risk of macular degeneration or blindness. On the other hand, looking directly at the point of high-powered LED lamps is potentially dangerous.

The review of Z. C. Chao, Y. Zhou, G. Tan, and J. Li reminded that to a certain extent, blue light exposure can be beneficial. For starters, it helps in regulating the circadian rhythm by aiding the secretion of melatonin during the daytime. In addition, it can promote human eye refractive development. Hence, more specific wavelengths of blue light are not harmful.

Manufacturers such as Apple and Microsoft have included features in their electronic devices that allow users to adjust the color temperature of the display toward a warmer gamut to reduced supposed eyestrain. However, doing so reduces the user experience by affecting color reproduction accuracy. Also, the eyestrain from using smartphones or computers is simply a phenomenon called digital eyestrain resulting from prolonged periods of using the eyes and not from exposure to blue light.

In the United Kingdom, it is illegal for ophthalmologists, optometrists, and other health care practitioners to tell patients that blue light within the 400 to 450 nm range can negatively affect sleep and cause health effects. In 2017, the U.K. Advertising Standards Authority fined Boots Optician, a chain of ophthalmic stores, for selling blue-light-filtering lenses and claiming that these products prevent eye diseases.

Summary and Takeaway

The verdict about the negative health effects of blue light exposure is considerably simple. Studies have shown that such an exposure form using electronic devices or lighting fixtures at nighttime can indeed affect the secretion of melatonin and disrupt the biological clock. Disrupted sleep has been linked to physical and mental health problems. However, no studies indicate that exposure from similar sources could result in eye damage.


  • Chang, A. M., Aeschbach, D., Duffy, J. F., and Czeisler, C. A. 2015. “Evening Use of Light-Emitting eReaders Negatively Affects Sleep, Circadian Timing, and Next-Morning Alertness.” PNAS. 112(4): 1232-1237. DOI: 10.1073/pnas.1418490112
  • Chao, Z. C., Zhou, Y., Tan, G., and Li, J. 2018. “Research Progress About the Effect and Prevention of Blue Light on Eyes.” International Journal of Ophthalmology. 11(12): 1999-2003. DOI: 10.18240/ijo.2018.12.20
  • Harvard Health Publishing. 2018, August 13. “Blue Light Has A Dark Side,” Harvard Health Letter. Harvard Health Publishing. Available online
  • Ramsey, D. 2019, April 8. “Will Blue Light from Electronic Devices Increase My Risk of Macular Degeneration and Blindness?” Harvard Health Blog. Harvard Health Publishing. Available online
  • Ratnayake, K., Payton, J. L., Lakmal, O. H., and Karunarathne, A. 2018. “Blue Light Excited Retinal Intercepts Cellular Signaling.” Scientific Reports. 8(1). DOI: 10.1038/s41598-018-28254-8
  • Tosini, G., Ferguson, I., and Tsubota, K. 2016. “Effects of Blue Light on the Circadian System and Eye Physiology.” Molecular Vision. 22: 61-72. PMID: 26900325
  • Woodley, M. 2015, May 31. “Optical Chain Fined $69,000 for Misleading Ad.” Insight. Available online