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Sunlight, Outdoor Light, and Light Therapy


Bright light and lack of sunlight can cause medical problems. This brief review highlights the role and practical use of light therapy sunlight and outdoor lighting as an adjuvant in pain depression and mood management.


Since ancient times, many ancient cultures have worshiped the sun for various reasons. Hippocrates wrote the first treatise on the psychiatric and psychological benefits of the sun and named this treatment Heliotherapy.[1] Taber’s Cyclopedic Medical Dictionary defines heliotherapy as invasive sunlight therapy and phototherapy as sunlight exposure or ultraviolet light therapy.[2] Phototherapy can be used to treat conditions such as diffuse atopic dermatitis diffuse seasonal and non-seasonal depression seasonal obsessive-compulsive disorder and excessive bilirubinemia in neonates.[3] From about the mid-19th century to the mid-20th century, sunlight combined with proper hygienic isolation saw fresh air for a healthy diet and exercise used to prevent and treat tuberculosis.[4] Also Niels Ryberg Finsen (1860-1904) . he won the Nobel Prize in Medicine in 1903 for his work on phototherapy for diseases such as lupus vulgaris.[5]

Light Therapy in Medicine

Outdoor Exercise

Sensible sunlight plays an important role in overall health. Michael F. Holick Ph.D. An MD researcher at Boston University Medical Center suggests that vitamin D is the sunshine vitamin and that sunlight plays a role in vitamin synthesis.[6][7][8][9]The use of sunlight can be effective in nevertheless health[10]prevents diseases[11]improves life expectancy[12]reduces mental illness[13]helps deal with influenza epidemics[14][15]builds immune response greatly[16]address the coronavirus[17]and improve employee mental health. 18] .

Additionally sunlight can have antimicrobial properties[19]and help reduce fungal contamination in contaminated clothing.[20]Light therapy can be used to address seasonal mood disorders[21]. for major depression and schizophrenia without a seasonal pattern[22]useful for development sleep-wake cycles in individuals with Parkinson’s disease[23]and multiple sclerosis-related fatigue.[24]

Light Therapy for Mood Disorders

An article by Turner and Mainster[25] in the British Journal of Ophthalmology suggests that eyes play an important role in good health. The authors state that “Bright light (≥2500 lux) especially from blue sources such as outdoor daylight can reduce or eliminate insomnia and depression; immediately increases brain serotonin emotional alertness and cognitive function.” A 1994 study in Biological Psychiatry[26] suggests that “many Americans may not be exposed to sufficient light to achieve optimal outlook.” Interestingly, the themes in this study had San Diego sunny California and between the ages of 40 and 64. According to Figueiro et al[27] “Light can also give people a strong ‘coffee cup’ alert.” A study during long in the Journal of Neural Transmission in 2007[28] concluded that blue light increases alertness and processing speed.

Light Therapy for Pain Management

A randomized study in Pain Medicine in 2014[29] suggests that light therapy can not only improve depressive symptoms but also reduce pain acuteness in individuals with chronic back pain who do not in the particular. The authors suggest that this effect may be due to similar shared pain and trauma pathways of infection. Another study by Burgess et al[30] suggests that morning light therapy may help US. veterans with chronic low back pain. Another study by the same senior author[31] suggests that light therapy may have potential as an alternative treatment for fibromyalgia. Table 1 summarizes the advantages of sunlight and solar radiation and Table 2 lists the amount of light available outdoors and indoors.

Table 1 – Benefits of sunlight and sunlight [4][6][8][9][14][16][19][20]Vitamin D sources

  • Sources of bright natural light to improve mood and periodic and irregular depression
  • Treatment of medical conditions such as tuberculosis and psoriasis
  • Controlling infections
  • Improve immune system
  • Bactericidal potential
  • Potential to reduce fungal contamination

Table 2 – Light levels outdoors and indoors.

  • Adapted from Choukroun et al[1] Turner et al[25].
  • Lux is the luminous intensity equal to 1 lumen/m2.[2]
Safety Considerations

Light therapy is generally safe for the eyes. However, individuals using light therapy should have periodic eye exams.[32][33][34]

Using a Light Therapy Box

Precautions for light therapy include headache weak or photosensitive light (due to glare and light sensitivity) photosynthetic skin lightening (e.g. psychiatric medication delivery). arthritis psoralen antiepileptic drugs antimalarials antiepileptic drugs medicines St. John’s Wort) and eye abnormalities.[35] Physicians should also be aware that individuals using light therapy may experience side effects such as anxiety blurred vision daytime drowsiness dry eyes strained eyes fatigue headaches excessive insomnia irritability seizures nor a phenomenon similar to sunburn.[32] [36] .

Practical Application

Outdoor activity exercises and work contribute to optimal light[37]. Table 3 lists outdoor activities for example sports exercise winter exercise and indoor exercise to improve brightness. Researchers have found that unhealthy lighting practices in the home[32] workplace[38] and schooling39[39] may affect performance[38] depression[32][40] sleep[41][42][43][43][44] and myopia.[45]

Table 3 – Examples of outdoor activities to increase internal brightness.

Places for Outdoor ActivitiesBalconyPatioBackyardGazeboParkTrailFitness court (e.g. pullup bars rope parallel bars rings)Outdoor ActivitiesBikingWalkingOutdoor calisthenicsOutdoor PilatesOutdoor tai chiOutdoor yogaWalkingOutdoor SportsBasketballPickleballSoftballTable tennisTennisVolleyballWinter ActivitiesCcross-country skiingIce skatingOutdoor road cyclingStreet walkingSkiingSled ridingSnowshoe walkingSnowboarding

Tables 4 5 and 6 show practical self-management strategies that can be used to increase light at homework or school.

Table 4 – Practical self-control strategies for increasing light levels in the home.

  • Get plenty of natural outdoor light during the day especially in the morning.
  • Eat your breakfast near the window or on the balcony patio or in your backyard gazebo.
  • Open the curtains to let in as much outdoor light as possible especially in the morning.
  • Consider remodeling the home to add more windows or skylights or enhance existing windows.
  • Consider adding a sunroom or gazebo to the backyard for exercise meditation relaxation or reading.
  • Consider painting walls in lighter shades or tones (e.g. white) and buy furniture in lighter colors.
  • Create a reading relaxation or healing space in your home that lets in the sunlight. It is best to let the sun shine behind the person when reading.
  • Orient a home computer or workstation toward a large window, where one can gaze into the distance now and then. However, homeowners should avoid direct sunlight.
  • Wash windows and prune shrubs and trees near windows to let more light into the house.
  • To prevent sleep problems, turn off your phone and computer a few hours before bed.
  • Sit on your balcony patio porch or backyard, bird watch or gaze at the horizon or distant trees for light and relaxation.

For the best bang for their buck, homeowners may want to consider remodeling their homes to allow for more interaction with the outdoor environment. Consult a sleep medicine or lighting specialist for additional guidance.

Table 5 – Practical self-management strategies for increasing task lighting

  • If one’s office has windows, then the desk should face out of the window. Being able to look away from your computer monitor and look into the distance may help reduce eye strain. But office workers should avoid direct sunlight.
  • Arrange all workstations around the perimeter of the office to face windows.
  • Place vending machines, water dispensers, and copiers near windows.
  • Hold meetings in a well-lit room with large windows and natural outdoor light.
  • Consider holding group meetings while walking outside on a sunny day.
  • Consider adding skylights in areas with many workstations.
  • Open the shutters and trim the shrubs and trees that cover the office windows.
  • Eat your lunch outside (on a picnic table or in a portable chair), even if someone is sitting under a tree or in the shade. If one cannot go outside due to heat or cold allergies or pollution, sit near a cafeteria window and watch birds or gaze at the horizon or trees in the distance.
  • Take a 10 to 15 minute walk after lunch. Get an outdoor workout before work, during lunch, or after get off work. Short bouts of exercise have been shown to be effective in improving health and enhancing exercise adherence in overweight and obese adults. [46][47]
  • Get outdoors during work breaks. Even on an overcast day, the outdoors provide more light than typical indoor office lighting (see Table 2 for lux levels).

For the best benefit, companies may want to consider retrofitting their buildings to allow for more interaction with the outdoor environment. Consult a sleep medicine or lighting specialist for additional guidance.

Table 6 – Practical self-management strategies for increasing light in schools.

  • Open the blinds and drapes to let in the natural light from outside.
  • Have the children sit near a window. But students should avoid direct sunlight.
  • Take recess outdoors.
  • Include activities that involve outdoor activities, such as gardening and sports.
  • Encourage children to eat outside, even under a tree or in the shade. If kids can’t go outside because of heat or cold allergies or pollution, have them sit near a cafeteria window and watch the birds or gaze into the distance.
  • Include more outdoor breaks and outdoor PE classes. According to some researchers, higher levels of total outdoor time may be associated with less myopia. [45]

For the best benefit, schools may need to consider retrofitting their buildings to allow for more interaction with the outdoor environment. Consult a sleep medicine or lighting specialist for additional guidance.

Assessment Tools
  • Morning and evening questionnaire (MEQ) Horne JA Ostberg O. Self-assessment questionnaire for determining morning and evening in human circadian rhythms. Int J Chronobiol. 1976;4(2):97-110. https://pubmed.ncbi.nlm.nih.gov/1027738/
  • Munich ChronoType Questionnaire (MCTQ Roenneberg T Wirz-Justice A Merrow M. Life Between Clocks: Everyday Time Patterns of Human Timetables. J Biol Rhythms. 2003;18(1):80-90. doi:10.1177/0748730402239679 https: https://pubmed.ncbi.nlm.nih.gov/12568247/
  • Seasonal health questionnaire (SHQ) Thompson C Cowan A. The seasonal health questionnaire: preliminary validation of a new tool for screening for seasonal affective disorder. J Impact Disorder. 2001;64(1):89-98. doi: 10.1016/s0165-0327(00)00208-1 https://pubmed.ncbi.nlm.nih.gov/11292523/
  • Seasonal Pattern Assessment Questionnaire (SPAQ) Mersch PP Vastenburg NC Meesters Y et al. Reliability and validity of a seasonal pattern assessment questionnaire: a comparison between patient groups. J Impact Disorder. 2004;80(2-3):209-219. doi:10.1016/S0165-0327(03)00114-9 https://pubmed.ncbi.nlm.nih.gov/15207934/
  • Murray G. The seasonal pattern assessment questionnaire as a measure of emotional seasonality: a prospective validation study. Psychiatric Research. 2003;120(1):53-59. doi:10.1016/s0165-1781(03)00147-1 https://pubmed.ncbi.nlm.nih.gov/14500114/
  • Rosenthal N. Bradt G. Wehr T. Seasonal Pattern Assessment Questionnaire (SPAQ) Bethesda, MD, USA: National Institute of Mental Health; 1984
Related Articles
  • Fifel K Videnovic A. Phototherapy in Parkinson’s disease: towards a mechanism-based approach. Trends in Neuroscience. 2018;41(5):252-254. doi:10.1016/j.tins.2018.03.002
  • Figueiro MG Gras LZ Rea MS Plitnick B Rea MS. Lighting to improve balance in older adults with and without risk of falls. aging. 2012;41(3):392-395. doi:10.1093/aging/afr166
  • Figueiro MG Plitnick B Roohan C Sahin L Kalsher M Rea MS. Effects of a tailored lighting intervention on sleep quality, rest activity, mood and behavior in older adults with Alzheimer’s disease and related dementias: a randomized clinical trial. J Clin Sleep Med. 2019;15(12):1757-1767. doi:10.5664/jcsm.8078
  • Figueiro MG Sahin L Kalsher M Plitnick B Rea MS. Chronic round-the-clock exposure to circadian-effective light improves sleep mood and behavior in people with dementia. J Alzheimers Dis Rep. 2020;4(1):297-312. doi:10.3233/ADR-200212
  • Holick M. F. Vitamin D deficiency. New England Journal of Medicine. 2007;357(3):266–281. Home Office: 10.1056/nejmra070553.
  • Lam RW Levitt AJ Levitan RD et al. Efficacy of intense light therapy with fluoxetine and combination therapy in patients with nonseasonal major depressive disorder: a randomized clinical trial [Correction published in JAMA Psychiatry. 2016 Jan;73(1):90]. JAMA Psychiatry. 2016;73(1):56-63. doi:10.1001/jamapsychiatry.2015.2235
  • Lunn RM Blask DE Coogan AN et al. Health effects of electrical lighting practices in the modern world: report of the National Toxicology Program Symposium on nighttime shift work with artificial light at night and circadian rhythm disturbances. Science comprehensive environment. 2017;607–608:1073–1084.
  • Steele TA St Louis EK Videnovic A Auger RR. Circadian rhythm sleep-wake disorders: a contemporary review of neurobiological treatments and disorders in neurodegenerative diseases. neurotherapeutics. 2021;18(1):53-74. doi:10.1007/s13311-021-01031-8


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  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
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  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 studyPain Med. 2017;18(1):116‐123. doi:10.1093/pm/pnw160
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  33.  Gallin PF, Terman M, Remé CE, Rafferty B, Terman JS, Burde RM. Ophthalmologic examination of patients with seasonal affective disorder, before and after bright light therapy. Am J Ophthalmol. 1995;119(2):202‐210. doi:10.1016/s0002-9394(14)73874-7
  34.  Remé CE, Rol P, Grothmann K, Kaase H, Terman M. Bright light therapy in focus: lamp emission spectra and ocular safety. Technol Health Care. 1996;4(4):403‐413.
  35.  Wirz-Justice A, Benedetti F, Terman M. Chronotherapeutics For Affective Disorders: A Clinician’s Manual for Light and Wake Therapy, 2nd ed. Basel: Karger; 2013.
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  37.  Hahn IH, Grynderup MB, Dalsgaard SB, et al. Does outdoor work during the winter season protect against depression and mood difficulties? Scand J Work Environ Health. 2011;37(5):446‐449. doi:10.5271/sjweh.3155
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  39.  Baloch RMM, Maesano CN, Christoffersen J, et al. Daylight and school performance in European schoolchildrenInt J Environ Res Public Health. 2020;18(1):258. doi:10.3390/ijerph18010258
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  41.  Youngstedt SD, Leung A, Kripke DF, Langer RD. Association of morning illumination and window covering with mood and sleep among post-menopausal women. Sleep Biol Rhythms. 2004;2(3):174‐183. doi:10.1111/j.1479-8425.2004.00139.x

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