Sunlight, Outdoor Light, and Light Therapy in Disease Management: Difference between revisions

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A lack of bright light and sunshine may lead to various medical disorders. This brief review highlights the role and practical application of light therapy, sunlight, and outdoor light exposure as an adjunct in managing pain, depression, and mood.
A lack of bright light and sunshine may lead to various medical disorders. This brief review highlights the role and practical application of light therapy, sunlight, and outdoor light exposure as an adjunct in managing pain, depression, and mood.


Since antiquity, many ancient cultures have worshipped the sun for a variety of reasons. Hippocrates wrote the first texts about the sun's benefits on mental health and mood and named this therapy "Heliotherapy."<ref>Choukroun J, Geoffroy PA. Light therapy in mood disorders: A brief history with physiological insights. ''Chronobiol Med''. 2019; 1(1):3-8. doi.org/10.33069/cim.2018.0009<nowiki/>https://www.chronobiologyinmedicine.org/journal/view.php?number=5</ref> ''Taber's Cyclopedic Medical Dictionary'' defines heliotherapy as "exposure to sunlight for therapeutic purposes" and phototherapy as "exposure to sunlight or to ultraviolet light for therapeutic purposes."<ref>Venes, D. ''Taber’s Cyclopedic Medical Dictionary, 23rd ed''. Philadelphia, A: F.A. Davis Company; 2017, pp. 1016, 1087, 1490, 2548.</ref> Phototherapy may be used to treat conditions such as extensive atopic dermatitis, extensive psoriasis, seasonal and nonseasonal depression, seasonal bipolar disorders, and neonatal hyperbilirubinemia.<ref>Porter RS, Kaplan JL, Lynn RB. ''The Merck Manual of Diagnosis and Therapy, 20<sup>th</sup> edition''. Kenilworth, NJ: Merck Sharp & Dohme Corp, 2018; 1023, 1072, 1741, 1757, 1761, 1767, 2729.</ref> From about the middle of the 19th century to the middle of the 20th century, sunlight, in combination with isolation, proper hygiene, fresh air, good nutrition, and physical exercise, was used to control and treat tuberculosis.<ref name=":0">McCullough PJ, Lehrer DS. [https://pubmed.ncbi.nlm.nih.gov/28756294/ Vitamin D, cod liver oil, sunshine, and phototherapy: Safe, effective and forgotten tools for treating and curing tuberculosis infections - A comprehensive review.] ''J Steroid Biochem Mol Biol''. 2018;177:21‐29. doi:10.1016/j.jsbmb.2017.07.027</ref> Moreover, Niels Ryberg Finsen (1860-1904) earned a Nobel Prize in Medicine in 1903 for his work on phototherapy to treat diseases such as lupus vulgaris.<ref>Grzybowski A, Pietrzak K. [https://pubmed.ncbi.nlm.nih.gov/22855977/ From patient to discoverer--Niels Ryberg Finsen (1860–1904) --the founder of phototherapy in dermatology.] ''Clin Dermatol''. 2012;30(4):451-455. doi:10.1016/j.clindermatol.2011.11.019</ref>
Since antiquity, many ancient cultures have worshipped the sun for a variety of reasons. Hippocrates wrote the first texts about the sun's benefits on mental health and mood and named this therapy "Heliotherapy."<ref name=":8">Choukroun J, Geoffroy PA. Light therapy in mood disorders: A brief history with physiological insights. ''Chronobiol Med''. 2019; 1(1):3-8. doi.org/10.33069/cim.2018.0009<nowiki/>https://www.chronobiologyinmedicine.org/journal/view.php?number=5</ref> ''Taber's Cyclopedic Medical Dictionary'' defines heliotherapy as "exposure to sunlight for therapeutic purposes" and phototherapy as "exposure to sunlight or to ultraviolet light for therapeutic purposes."<ref name=":9">Venes, D. ''Taber’s Cyclopedic Medical Dictionary, 23rd ed''. Philadelphia, A: F.A. Davis Company; 2017, pp. 1016, 1087, 1490, 2548.</ref> Phototherapy may be used to treat conditions such as extensive atopic dermatitis, extensive psoriasis, seasonal and nonseasonal depression, seasonal bipolar disorders, and neonatal hyperbilirubinemia.<ref>Porter RS, Kaplan JL, Lynn RB. ''The Merck Manual of Diagnosis and Therapy, 20<sup>th</sup> edition''. Kenilworth, NJ: Merck Sharp & Dohme Corp, 2018; 1023, 1072, 1741, 1757, 1761, 1767, 2729.</ref> From about the middle of the 19th century to the middle of the 20th century, sunlight, in combination with isolation, proper hygiene, fresh air, good nutrition, and physical exercise, was used to control and treat tuberculosis.<ref name=":0">McCullough PJ, Lehrer DS. [https://pubmed.ncbi.nlm.nih.gov/28756294/ Vitamin D, cod liver oil, sunshine, and phototherapy: Safe, effective and forgotten tools for treating and curing tuberculosis infections - A comprehensive review.] ''J Steroid Biochem Mol Biol''. 2018;177:21‐29. doi:10.1016/j.jsbmb.2017.07.027</ref> Moreover, Niels Ryberg Finsen (1860-1904) earned a Nobel Prize in Medicine in 1903 for his work on phototherapy to treat diseases such as lupus vulgaris.<ref>Grzybowski A, Pietrzak K. [https://pubmed.ncbi.nlm.nih.gov/22855977/ From patient to discoverer--Niels Ryberg Finsen (1860–1904) --the founder of phototherapy in dermatology.] ''Clin Dermatol''. 2012;30(4):451-455. doi:10.1016/j.clindermatol.2011.11.019</ref>


== Light Therapy in Medicine ==
== Light Therapy in Medicine ==
Line 21: Line 21:
== Light Therapy for Mood Disorders ==
== Light Therapy for Mood Disorders ==


An article by Turner and Mainster<ref>Turner PL, Mainster MA. [https://pubmed.ncbi.nlm.nih.gov/18757473/ Circadian photoreception: ageing and the eye's important role in systemic health.] ''Br J Ophthalmol''. 2008;92(11):1439‐1444. doi:10.1136/bjo.2008.141747</ref> in the ''British Journal of Ophthalmology'' indicates that the eyes play a vital role in good health. The authors state that “Bright light (≥2500 lux), particularly from bluer sources such as outdoor daylight, can reduce or eliminate insomnia and depression; immediately increase brain serotonin, mood, alertness, and cognitive function.” A study in ''Biological Psychiatry'' in 1994<ref>Espiritu RC, Kripke DF, Ancoli-Israel S, et al. [https://pubmed.ncbi.nlm.nih.gov/8018787/ Low illumination experienced by San Diego adults: association with atypical depressive symptoms.] ''Biol Psychiatry''. 1994;35(6):403‐407. doi:10.1016/0006-3223(94)90007-8</ref> indicates that “many Americans may be receiving insufficient light exposure to maintain optimal mood.” Interestingly, the subjects in this study were located in sunny San Diego, California, and 40 to 64 years old. According to Figueiro and colleagues,<ref>Figueiro MG, Nagare R, Price L. [https://pubmed.ncbi.nlm.nih.gov/30416392/ Non-visual effects of light: how to use light to promote circadian entrainment and elicit alertness.] ''Light Res Technol''. 2018;50(1):38-62. doi:10.1177/1477153517721598</ref> “Light can also elicit an acute alerting effect on people, similar to a ‘cup of coffee.’” A longitudinal study in the ''Journal of Neural Transmission'' in 2007<ref>Lehrl S, Gerstmeyer K, Jacob JH, et al. [https://pubmed.ncbi.nlm.nih.gov/17245536/ Blue light improves cognitive performance.] ''J Neural Transm (Vienna)''. 2007;114(4):457‐460. doi:10.1007/s00702-006-0621-4</ref> concluded that blue light increases alertness and information processing speed.
An article by Turner and Mainster<ref name=":10">Turner PL, Mainster MA. [https://pubmed.ncbi.nlm.nih.gov/18757473/ Circadian photoreception: ageing and the eye's important role in systemic health.] ''Br J Ophthalmol''. 2008;92(11):1439‐1444. doi:10.1136/bjo.2008.141747</ref> in the ''British Journal of Ophthalmology'' indicates that the eyes play a vital role in good health. The authors state that “Bright light (≥2500 lux), particularly from bluer sources such as outdoor daylight, can reduce or eliminate insomnia and depression; immediately increase brain serotonin, mood, alertness, and cognitive function.” A study in ''Biological Psychiatry'' in 1994<ref>Espiritu RC, Kripke DF, Ancoli-Israel S, et al. [https://pubmed.ncbi.nlm.nih.gov/8018787/ Low illumination experienced by San Diego adults: association with atypical depressive symptoms.] ''Biol Psychiatry''. 1994;35(6):403‐407. doi:10.1016/0006-3223(94)90007-8</ref> indicates that “many Americans may be receiving insufficient light exposure to maintain optimal mood.” Interestingly, the subjects in this study were located in sunny San Diego, California, and 40 to 64 years old. According to Figueiro and colleagues,<ref>Figueiro MG, Nagare R, Price L. [https://pubmed.ncbi.nlm.nih.gov/30416392/ Non-visual effects of light: how to use light to promote circadian entrainment and elicit alertness.] ''Light Res Technol''. 2018;50(1):38-62. doi:10.1177/1477153517721598</ref> “Light can also elicit an acute alerting effect on people, similar to a ‘cup of coffee.’” A longitudinal study in the ''Journal of Neural Transmission'' in 2007<ref>Lehrl S, Gerstmeyer K, Jacob JH, et al. [https://pubmed.ncbi.nlm.nih.gov/17245536/ Blue light improves cognitive performance.] ''J Neural Transm (Vienna)''. 2007;114(4):457‐460. doi:10.1007/s00702-006-0621-4</ref> concluded that blue light increases alertness and information processing speed.


== Light Therapy for Pain Management ==
== Light Therapy for Pain Management ==
A randomized study in ''Pain Medicine'' in 2014<ref>Leichtfried V, Matteucci Gothe R, Kantner-Rumplmair W, et al. [https://pubmed.ncbi.nlm.nih.gov/25159085/ Short-term effects of bright light therapy in adults with chronic nonspecific back pain: a randomized controlled trial.] ''Pain Med''. 2014;15(12):2003‐2012. doi:10.1111/pme.12503</ref> indicates that light therapy could not only improve depressive symptoms but also reduce pain intensity in individuals with chronic nonspecific back pain. The authors say that this effect may be due to pain and depression sharing similar pathophysiological pathways. Another study by Burgess and colleagues<ref>Burgess HJ, Rizvydeen M, Kimura M, et al. [https://pubmed.ncbi.nlm.nih.gov/30204903/ An open trial of morning bright light treatment among US military veterans with chronic low back pain: a pilot study]. ''Pain Med''. 2019;20(4):770‐778. doi:10.1093/pm/pny174</ref> shows that morning light therapy may help U.S. veterans with chronic low back pain. Another research study by the same lead author<ref>Burgess HJ, Park M, Ong JC, Shakoor N, Williams DA, Burns J. [https://pubmed.ncbi.nlm.nih.gov/27473633/ Morning versus evening bright light treatment at home to improve function and pain sensitivity for women with fibromyalgia: a pilot study]. ''Pain Med''. 2017;18(1):116‐123. doi:10.1093/pm/pnw160</ref> shows that light therapy may be feasible as an adjunctive treatment for fibromyalgia. Table 1 summarizes the benefits of sunshine and sunlight and Table 2 outlines light levels in outdoor and indoor environments.
A randomized study in ''Pain Medicine'' in 2014<ref>Leichtfried V, Matteucci Gothe R, Kantner-Rumplmair W, et al. [https://pubmed.ncbi.nlm.nih.gov/25159085/ Short-term effects of bright light therapy in adults with chronic nonspecific back pain: a randomized controlled trial.] ''Pain Med''. 2014;15(12):2003‐2012. doi:10.1111/pme.12503</ref> indicates that light therapy could not only improve depressive symptoms but also reduce pain intensity in individuals with chronic nonspecific back pain. The authors say that this effect may be due to pain and depression sharing similar pathophysiological pathways. Another study by Burgess and colleagues<ref>Burgess HJ, Rizvydeen M, Kimura M, et al. [https://pubmed.ncbi.nlm.nih.gov/30204903/ An open trial of morning bright light treatment among US military veterans with chronic low back pain: a pilot study]. ''Pain Med''. 2019;20(4):770‐778. doi:10.1093/pm/pny174</ref> shows that morning light therapy may help U.S. veterans with chronic low back pain. Another research study by the same lead author<ref>Burgess HJ, Park M, Ong JC, Shakoor N, Williams DA, Burns J. [https://pubmed.ncbi.nlm.nih.gov/27473633/ Morning versus evening bright light treatment at home to improve function and pain sensitivity for women with fibromyalgia: a pilot study]. ''Pain Med''. 2017;18(1):116‐123. doi:10.1093/pm/pnw160</ref> shows that light therapy may be feasible as an adjunctive treatment for fibromyalgia. Table 1 summarizes the benefits of sunshine and sunlight and Table 2 outlines light levels in outdoor and indoor environments.


Table 1.
'''Table 1.'''


Benefits of sunshine and sunlight <ref name=":0" /><ref name=":1" /><ref name=":2" /><ref name=":3" /><ref name=":4" /><ref name=":5" /><ref name=":6" /><ref name=":7" />
Benefits of sunshine and sunlight <ref name=":0" /><ref name=":1" /><ref name=":2" /><ref name=":3" /><ref name=":4" /><ref name=":5" /><ref name=":6" /><ref name=":7" />
Line 44: Line 44:
Potential to reduce fungal contamination
Potential to reduce fungal contamination
|}
|}
'''Table 2.'''
Light levels in outdoor and indoor environments.
{| class="wikitable"
|<sup>Outdoor Light Levels25</sup>
Bright sunlight, noon
Cloudy bright day
Overcast day
Very overcast day
Sun rising over the horizon
<sup>Indoor Light Levels25</sup>
<sup>Candle1</sup>
Offices, kitchens
Living room
Average nursing home
<sup>Typical Seasonal Affective Disorder (SAD) treatment1</sup>
|100,000 lux
25,000 lux
10,000 lux
2,000 lux
800 lux
1 lux
200-500 lux
50-200 lux
50 lux
2,500 lux (2 hours per day) or
5,000 lux (1 hour) or
10,000 lux (30 minutes per day)
|}
Adapted from Choukroun et al<ref name=":8" />, Turner et al<ref name=":10" />
Lux is a unit of light intensity equivalent to 1 lumen/m<sup>2</sup>.<ref name=":9" />


== References  ==
== References  ==

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Introduction[edit | edit source]

A lack of bright light and sunshine may lead to various medical disorders. This brief review highlights the role and practical application of light therapy, sunlight, and outdoor light exposure as an adjunct in managing pain, depression, and mood.

Since antiquity, many ancient cultures have worshipped the sun for a variety of reasons. Hippocrates wrote the first texts about the sun's benefits on mental health and mood and named this therapy "Heliotherapy."[1] Taber's Cyclopedic Medical Dictionary defines heliotherapy as "exposure to sunlight for therapeutic purposes" and phototherapy as "exposure to sunlight or to ultraviolet light for therapeutic purposes."[2] Phototherapy may be used to treat conditions such as extensive atopic dermatitis, extensive psoriasis, seasonal and nonseasonal depression, seasonal bipolar disorders, and neonatal hyperbilirubinemia.[3] From about the middle of the 19th century to the middle of the 20th century, sunlight, in combination with isolation, proper hygiene, fresh air, good nutrition, and physical exercise, was used to control and treat tuberculosis.[4] Moreover, Niels Ryberg Finsen (1860-1904) earned a Nobel Prize in Medicine in 1903 for his work on phototherapy to treat diseases such as lupus vulgaris.[5]

Light Therapy in Medicine[edit | edit source]

Sensible sunshine exposure plays an essential role in overall health. Michael F. Holick, Ph.D., MD, a researcher at the Boston University Medical Center, indicates that "vitamin D is the sunshine vitamin" and sunlight plays a role in vitamin synthesis.[6][7][8][9]Sunlight exposure may improve overall health,[10]control infections,[11]improve life expectancy,[12]reduce cognitive impairment,[13]help manage influenza pandemics[14][15]enhance the immune system,[16]manage coronavirus,[17]and improve employee mental health.[18]

Moreover, sunlight may have bactericidal potential[19]and help reduce fungal contamination in contaminated clothes.[20]Light therapy may be used to manage seasonal affective disorder,[21]for major depressive disorders and bipolar depression without seasonal pattern,[22]beneficial for improving sleep-wake cycles in individuals with Parkinson's disease,[23]and for multiple sclerosis-related fatigue.[24]

Light Therapy for Mood Disorders[edit | edit source]

An article by Turner and Mainster[25] in the British Journal of Ophthalmology indicates that the eyes play a vital role in good health. The authors state that “Bright light (≥2500 lux), particularly from bluer sources such as outdoor daylight, can reduce or eliminate insomnia and depression; immediately increase brain serotonin, mood, alertness, and cognitive function.” A study in Biological Psychiatry in 1994[26] indicates that “many Americans may be receiving insufficient light exposure to maintain optimal mood.” Interestingly, the subjects in this study were located in sunny San Diego, California, and 40 to 64 years old. According to Figueiro and colleagues,[27] “Light can also elicit an acute alerting effect on people, similar to a ‘cup of coffee.’” A longitudinal study in the Journal of Neural Transmission in 2007[28] concluded that blue light increases alertness and information processing speed.

Light Therapy for Pain Management[edit | edit source]

A randomized study in Pain Medicine in 2014[29] indicates that light therapy could not only improve depressive symptoms but also reduce pain intensity in individuals with chronic nonspecific back pain. The authors say that this effect may be due to pain and depression sharing similar pathophysiological pathways. Another study by Burgess and colleagues[30] shows that morning light therapy may help U.S. veterans with chronic low back pain. Another research study by the same lead author[31] shows that light therapy may be feasible as an adjunctive treatment for fibromyalgia. Table 1 summarizes the benefits of sunshine and sunlight and Table 2 outlines light levels in outdoor and indoor environments.

Table 1.

Benefits of sunshine and sunlight [4][6][8][9][14][16][19][20]

Source of vitamin D

Source of natural bright light to improve mood and seasonal and nonseasonal depression

Treating medical conditions such as tuberculosis and psoriasis

Controlling infections

Improve immune system

Bactericidal potential

Potential to reduce fungal contamination

Table 2.

Light levels in outdoor and indoor environments.

Outdoor Light Levels25

Bright sunlight, noon

Cloudy bright day

Overcast day

Very overcast day

Sun rising over the horizon

Indoor Light Levels25

Candle1

Offices, kitchens

Living room

Average nursing home

Typical Seasonal Affective Disorder (SAD) treatment1

100,000 lux

25,000 lux

10,000 lux

2,000 lux

800 lux

1 lux

200-500 lux

50-200 lux

50 lux

2,500 lux (2 hours per day) or

5,000 lux (1 hour) or

10,000 lux (30 minutes per day)

Adapted from Choukroun et al[1], Turner et al[25]

Lux is a unit of light intensity equivalent to 1 lumen/m2.[2]

References [edit | edit source]

  1. 1.0 1.1 Choukroun J, Geoffroy PA. Light therapy in mood disorders: A brief history with physiological insights. Chronobiol Med. 2019; 1(1):3-8. doi.org/10.33069/cim.2018.0009https://www.chronobiologyinmedicine.org/journal/view.php?number=5
  2. 2.0 2.1 Venes, D. Taber’s Cyclopedic Medical Dictionary, 23rd ed. Philadelphia, A: F.A. Davis Company; 2017, pp. 1016, 1087, 1490, 2548.
  3. Porter RS, Kaplan JL, Lynn RB. The Merck Manual of Diagnosis and Therapy, 20th edition. Kenilworth, NJ: Merck Sharp & Dohme Corp, 2018; 1023, 1072, 1741, 1757, 1761, 1767, 2729.
  4. 4.0 4.1 McCullough PJ, Lehrer DS. Vitamin D, cod liver oil, sunshine, and phototherapy: Safe, effective and forgotten tools for treating and curing tuberculosis infections - A comprehensive review. J Steroid Biochem Mol Biol. 2018;177:21‐29. doi:10.1016/j.jsbmb.2017.07.027
  5. Grzybowski A, Pietrzak K. From patient to discoverer--Niels Ryberg Finsen (1860–1904) --the founder of phototherapy in dermatology. Clin Dermatol. 2012;30(4):451-455. doi:10.1016/j.clindermatol.2011.11.019
  6. 6.0 6.1 Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004;80(6 Suppl):1678S-88S. doi:10.1093/ajcn/80.6.1678S
  7. Holick MF. The Vitamin D Solution. New York, NY: Plume; 2010: 157-196.
  8. 8.0 8.1 Holick MF. Biological effects of sunlight, ultraviolet radiation, visible light, infrared radiation and vitamin D for health. Anticancer Res. 2016;36(3):1345‐1356.
  9. 9.0 9.1 Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermatoendocrinol. 2013;5(1):51-108. doi:10.4161/derm.24494
  10. Baggerly CA, Cuomo RE, French CB, et al. Sunlight and vitamin D: Necessary for public health. J Am Coll Nutr. 2015;34(4):359‐365. doi:10.1080/07315724.2015.1039866
  11. Hobday RA, Dancer SJ. Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives. J Hosp Infect. 2013;84(4):271-282. doi:10.1016/j.jhin.2013.04.01
  12. Lindqvist PG, Epstein E, Nielsen K, Landin-Olsson M, Ingvar C, Olsson H. Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort. J Intern Med. 2016;280(4):375-387. doi:10.1111/joim.12496
  13. Kent ST, McClure LA, Crosson WL, Arnett DK, Wadley VG, Sathiakumar N. Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study. Environ Health. 2009;8:34. doi:10.1186/1476-069X-8-34
  14. 14.0 14.1 Hobday RA, Cason JW. The open-air treatment of pandemic influenza. Am J Public Health. 2009;99 Suppl 2(Suppl 2):S236-S242. doi:10.2105/AJPH.2008.134627
  15. Schuit M, Gardner S, Wood S, et al. The influence of simulated sunlight on the inactivation of influenza virus in aerosols. J Infect Dis. 2020;221(3):372-378. doi:10.1093/infdis/jiz582
  16. 16.0 16.1 González Maglio, D. H., Paz, M. L., & Leoni, J. (2016). Sunlight effects on immune system: is there something else in addition to UV-Induced immunosuppression?. BioMed Res Int, 2016, 1934518. doi.org/10.1155/2016/1934518
  17. Tang L, Liu M, Ren B, et al. Sunlight ultraviolet radiation dose is negatively correlated with the percent positive of SARS-CoV-2 and four other common human coronaviruses in the U.S. Sci Total Environ. 2021;751:141816. doi:10.1016/j.scitotenv.2020.141816
  18. An M, Colarelli SM, O'Brien K, Boyajian ME. Why we need more nature at work: effects of natural elements and sunlight on employee mental health and work attitudes. PLoS One. 2016;11(5):e0155614. doi:10.1371/journal.pone.0155614
  19. 19.0 19.1 Fahimipour AK, Hartmann EM, Siemens A, et al. Daylight exposure modulates bacterial communities associated with household dust. Microbiome. 2018;6(1):175. doi:10.1186/s40168-018-0559-4
  20. 20.0 20.1 Amichai B, Grunwald MH, Davidovici B, Shemer A. "Sunlight is said to be the best of disinfectants:" The efficacy of sun exposure for reducing fungal contamination in used clothes. Isr Med Assoc J. 2014;16(7):431‐433.
  21. Terman M, Terman JS, Ross DC. A controlled trial of timed bright light and negative air ionization for treatment of winter depression. Arch Gen Psychiatry. 1998;55(10):875‐882. doi:10.1001/archpsyc.55.10.875
  22. Penders TM, Stanciu CN, Schoemann AM, Ninan PT, Bloch R, Saeed SA. Bright light therapy as augmentation of pharmacotherapy for treatment of depression: a systematic review and meta-analysis. Prim Care Companion CNS Disord. 2016;18(5):10.4088/PCC.15r01906.
  23. Videnovic A, Klerman EB, Wang W, Marconi A, Kuhta T, Zee PC. Timed light therapy for sleep and daytime sleepiness associated with Parkinson disease: a randomized clinical trial. JAMA Neurol. 2017;74(4):411‐418.
  24. Mateen FJ, Vogel AC, Kaplan TB, et al. Light therapy for multiple sclerosis-associated fatigue: a randomized, controlled phase II trial. J Neurol. 2020;267(8):2319-2327. doi:10.1007/s00415-020-09845-w
  25. 25.0 25.1 Turner PL, Mainster MA. Circadian photoreception: ageing and the eye's important role in systemic health. Br J Ophthalmol. 2008;92(11):1439‐1444. doi:10.1136/bjo.2008.141747
  26. Espiritu RC, Kripke DF, Ancoli-Israel S, et al. Low illumination experienced by San Diego adults: association with atypical depressive symptoms. Biol Psychiatry. 1994;35(6):403‐407. doi:10.1016/0006-3223(94)90007-8
  27. Figueiro MG, Nagare R, Price L. Non-visual effects of light: how to use light to promote circadian entrainment and elicit alertness. Light Res Technol. 2018;50(1):38-62. doi:10.1177/1477153517721598
  28. Lehrl S, Gerstmeyer K, Jacob JH, et al. Blue light improves cognitive performance. J Neural Transm (Vienna). 2007;114(4):457‐460. doi:10.1007/s00702-006-0621-4
  29. Leichtfried V, Matteucci Gothe R, Kantner-Rumplmair W, et al. Short-term effects of bright light therapy in adults with chronic nonspecific back pain: a randomized controlled trial. Pain Med. 2014;15(12):2003‐2012. doi:10.1111/pme.12503
  30. Burgess HJ, Rizvydeen M, Kimura M, et al. An open trial of morning bright light treatment among US military veterans with chronic low back pain: a pilot study. Pain Med. 2019;20(4):770‐778. doi:10.1093/pm/pny174
  31. Burgess HJ, Park M, Ong JC, Shakoor N, Williams DA, Burns J. Morning versus evening bright light treatment at home to improve function and pain sensitivity for women with fibromyalgia: a pilot study. Pain Med. 2017;18(1):116‐123. doi:10.1093/pm/pnw160