Light Therapy: Does It Work for Sleep Disorders?

  • Simone Marie Ota Doctor of Philosophy - PhD in Science, University of Groningen (Netherlands) and Federal University of Sao Paulo (Brazil)

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Introduction

Sleep disorders are a group of conditions that affect normal sleep timing, duration, or quality in which interfere with how you function when awake. In other words, if you have a sleep disorder, you can’t sleep when you are supposed to, and you don’t feel restored the next day. This can impact your physical, mental, social, and emotional performance. Therefore, sleep disorders can affect health and quality of life.1

Light is an important factor that helps regulate sleep and wakefulness. For this reason, light therapy has been designed to treat certain sleep disorders through exposure to artificial light using a special device (light therapy box).2 

Light therapy can help people with sleep problems related to:

Understanding light therapy

Light therapy can be done at home. Each day you sit in front of the light box or visor developed for light therapy for the amount of time prescribed by your doctor. It is important to avoid direct light into your eyes to prevent any damage. 

A typical light box is commonly used:

  •  With a light intensity of 10,000 lux, similar to natural daylight, but without the UV rays
  •  16 to 24 inches (41 to 61 cm) away from the face
  •  For a duration of 20 to 40 minutes

You can do your other daily tasks during light therapy, such as reading, using your computer, talking on the phone, etc. When done correctly and consistently, light therapy can adjust your body’s internal clock and help you either sleep earlier or later, depending on your needs.

Types of light devices

There are different types of light apparatus developed for light therapy, in various sizes and shapes, such as:

  • Light box - Contains light tubes that can produce 10,000 lux of light, with some models focussing on specific wavelengths. The most commonly used
  • Desk lamp - Looks like a typical desk lamp, but has the same purpose as a light box
  • Wearable visor - Worn on your head and looks like a tennis visor. It allows you to walk around during sessions 
  • Dawn simulator - Brightens the room gradually to mimic the sunrise and can help people wake up in the morning

Mechanism of action

Most people have a set time when they feel alert, hungry, tired, etc. This happens because our body has an ‘internal clock’, or circadian rhythm, that regulates our physiological rhythms, such as eating and digesting, hormonal activity, body temperature, and sleep cycle. 

Typically, a healthy person wakes up in the morning and their tiredness increases as the daylight decreases. When it is dark our body produces melatonin, a hormone that induces sleep. Melatonin production is inhibited when there is light, making you feel more alert.2

However, if you have circadian-related sleep issues your body clock may function “behind” or “ahead” (delayed or advanced sleep-wake disorders). As light is the strongest signal to reset your body clock, light therapy can help you realign your circadian rhythm so you feel alert in the morning and sleepy at night. 

Effectiveness for common sleep disorders

Insomnia

Insomnia is a condition characterised by difficulty in falling asleep, staying asleep, or having poor sleep quality that results in dysfunction during the day.3 About 10% to 15% of the general population are said to have insomnia. Long-term, insomnia can affect health and productivity, increase daytime sleepiness and irritability, as well as impact quality of life.3

Currently, there is no ideal medication to treat insomnia. Sleeping pills can help induce sleep, but may cause side effects such as memory difficulties, daytime sleepiness, and dependency.4

Studies on insomnia and light therapy vary vastly, which prevents researchers from drawing conclusions on the effectiveness of this therapy for insomnia. It appears that light therapy can help maintain sleep, however, research has found that combining it with different interventions (like sleep hygiene, cognitive behavioural therapy, or melatonin) could be more effective.4

Circadian rhythm sleep disorders

This group of conditions occurs because your body clock is not synchronised to the time you go to sleep. It can develop naturally or by working night shifts.2

Delayed sleep phase disorder

If you have this disorder, your body clock is delayed in comparison to the majority of the population, you usually fall asleep much later at night and wake up later in the morning than most people. In other words, you have insomnia at night and excessive sleepiness in the morning. Consequently, it can impair your morning activities. To reset your body clock and correct this disorder, you can use bright light therapy in the morning and avoid artificial light in the evening. This will help you sleep earlier.2 

A review of studies showed that in general, light therapy helped participants sleep earlier, reduce wake times, and improve sleep quality. However, more studies are needed to obtain more conclusive data about the long-term effects of light therapy.5

Advanced sleep phase disorder

In contrast, if you have advanced sleep phase disorder, your body clock is ahead compared to real-time. You fall asleep much earlier at night than most people.2 People with this disorder have excessive sleepiness in the evening and wake up very early in the morning.2

To correct this disorder with light therapy, light exposure is done in the evening which delays your sleep and improves early-morning awakening. You should also avoid exposure to bright light in the morning after waking.2 Similarly, more studies are still needed to investigate how effective light therapy is for this condition. 

Free-running or non-24-hour sleep-wake rhythm disorder

This is where your body rhythm may have a period longer than 24 hours, causing you to fall asleep later each day. For example, one day, you might fall asleep at 10:00 p.m., but the next day, you fall asleep at midnight, and then at 2:00 a.m. the day after.6

This condition is rare and is more common in blind people. The appropriate treatment for non-24-hour sleep-wake rhythm disorder depends on the underlying cause. Although studies show that light therapy may be useful in the early morning hours, even for blind people (if they have functional neural pathways responsible for light reception and transmission), it is usually combined with melatonin treatment.6

Jet lag

Jet lag occurs when you travel across time zones, but your body’s clock remains in time with your previous location. It is temporary, but until your internal clock catches up to the time of the new location, you may have insomnia, excessive daytime sleepiness, and feel a bit uneasy.2

Although spending time outside and receiving natural sunlight can be enough to treat jet lag, light therapy may speed up the process. The time to use light therapy to treat jet lag depends on the direction of the flight. 

When travelling:

  • To the east, use light therapy in the morning
  • To the west, use light therapy in the evening2

However, there are few studies on the efficacy of light interventions for the treatment of jet lag and they are not conclusive. In laboratory conditions, light therapy has shown some effect and the results were better when combined with melatonin treatment.7

Shift work sleep disorder

This disorder occurs when you work when most people are sleeping, such as on the night shift.  About 15% to 20% of the working population in Europe and the US work on night shifts. One of the main complaints of shift workers is sleep disturbance, with a high percentage of them having insomnia and mental disorders. Shift work is also associated with more accidents, cardiovascular diseases, gastrointestinal dysfunction, type 2 diabetes, and cancer.2,8

Treating shift work disorder depends on the your schedule and it can be challenging when your social activities alter your exposure to light. In general, if you regularly work at night, you can use bright light therapy in the evening (4,000–7,000 lux for 4 hours) and also use sunglasses to avoid daylight in the morning.2 

Most studies on the effects of light therapy focus on night-shift workers and vary in terms of exposure time, light intensity, and equipment used.2,8 Nonetheless, research shows that light therapy can improve sleep and appears more effective than the cognitive behavioural approach, but no different from using medicine. On the other hand, light therapy has no continuous effect on the brain as medication can have.8

Safety considerations

If done as recommended, light therapy is considered very safe. Nevertheless, some patients might have minor side effects, including:

  • Eye irritation and dryness
  • Dryness of skin
  • Headache
  • Nausea

Always consult your doctor before starting light therapy, especially if you have bipolar disorder or any skin or eye condition that makes you more sensitive to sunlight. To prevent or reduce these side effects, begin the light therapy slowly and use a humidifier to help with any irritation caused by dryness.

Attention! 

Some light therapy boxes are meant to treat skin disorders like psoriasis and don’t have a UV light filter. Lightboxes to treat sleep disorders usually filter out UV light to avoid eye damage.

Summary

Light therapy, which involves exposure to artificial bright light, can be effective for insomnia and circadian rhythm sleep disorders. Since light influences the body's internal clock and inhibits melatonin, this therapy can help you reset your body clock, making you feel alert in the morning and sleepy at night. Sleep disorders are conditions that affect normal sleep patterns and can cause impact on physical, mental, and emotional well-being.

Although more studies are needed to show the effectiveness of light therapy on sleep disorders, various studies show that it can be promising for treating insomnia by maintaining and improving sleep quality. It may also help with circadian rhythm sleep disorders such as delayed sleep phase disorder, jet lag, and shift work sleep disorder.

References

  1. Karna B, Sankari A, Tatikonda G. Sleep disorder. Em: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jan 24]. Available from:  http://www.ncbi.nlm.nih.gov/books/NBK560720/
  2. Lee J, Lee J, Kim SJ. Current and future perspectives on light therapy using wearable devices. Chronobiol Med. 2021;3(3):92-96.[cited 2024 Jan 24]. Available from:http://chronobiologyinmedicine.org/journal/view.php?doi=10.33069/cim.2021.0019
  3. Kaur H, Spurling BC, Bollu PC. Chronic insomnia.In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024. [cited 2024 Jan 25]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK526136/
  4. Chambe J, Reynaud E, Maruani J, Fraih E, Geoffroy PA, Bourgin P. Light therapy in insomnia disorder: A systematic review and meta‐analysis. Journal of Sleep Research. 2023 ;32(6):e13895. Available from: https://onlinelibrary.wiley.com/doi/10.1111/jsr.13895
  5. Gomes JN, Dias C, Brito RS, Lopes JR, Oliveira IA, Silva AN, et al. Light therapy for the treatment of delayed sleep-wake phase disorder in adults: a systematic review. Sleep Sci. 2021;14(2):155–63. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8340891/
  6. Abbott SM. Non-24-hour sleep-wake rhythm disorder. Neurol Clin.2019;37(3):545–52.Available from: https://www.sciencedirect.com/science/article/pii/S0733861919300192
  7. Roach GD, Sargent C. Interventions to minimize jet lag after westward and eastward flight. Front Physiol. 2019;10:927. Available from: https://www.frontiersin.org/article/10.3389/fphys.2019.00927/full
  8. Jeon BM, Kim SH, Shin SH. Effectiveness of sleep interventions for rotating night shift workers: a systematic review and meta-analysis. Front Public Health. 2023 ;11:1187382. Available from: https://www.frontiersin.org/articles/10.3389/fpubh.2023.1187382/full

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Simone Marie Ota

Doctor of Philosophy - PhD in Science, University of Groningen (Netherlands) and Federal University of Sao Paulo (Brazil)

Simone is a curious motivated and analytical person with a passion for transforming complex scientific data into friendly and visual content. She has dedicated her career to the research of sleep, circadian rhythms and stress, and now she is also engaging in scientific and medical communication for all types of audiences.

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
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