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What you Need to Know About Light Therapy for Sleep Disorders

Adverse effects of sleep deprivation

  • Sleep deprivation can lead to a buildup of oxidative stress and inflammation, which can damage our mitochondria.

Uses of a SAD lamp

  • During the winter, getting a good night’s sleep can be more difficult to achieve, especially if you live farther north where the morning light is not as bright. SAD lamps, or seasonal affective disorder lamps, are lamps that simulate sunlight and can help to adjust our circadian rhythm, which in turn can improve the quality of our sleep.
  • Indeed, a meta-analysis reported that light therapy is effective for sleep problems, particularly for circadian outcomes and insomnia symptoms. However, most subject sizes studied were small to medium.
  • Other uses
    • SAD lamps have also been proven effective in treating seasonal affective disorder with efficiency comparable to fluoxetine, an antidepressant, and recently, non-seasonal depression. Natural bright light also improved mood status, ‘pleasantness’, and/or anger within 15–30 minutes of treatment. Several studies have also reported improvements in alertness, attention, and vigilance, especially during adverse conditions, after brief exposure to light.

How it works 

  • The mechanism of action remains unclear. There are two hypotheses:
    • One of the hypotheses is that the use of SAD lights corrects the winter circadian rhythm phase delay. During the winter, sunrises occur later and sunsets earlier than during the summer, which drifts later the circadian rhythm. Exposure to bright lights in the morning with SAD lights causes a circadian phase advance, making us feel more sleepy earlier in the evening.
    • Another hypothesis is that SAD lights work by increasing serotonin levels, which is also why light therapy can improve depressive symptoms. Serotonin is a hormone that plays a role in mood, sleep, appetite, memory, and energy levels, among others. Serotonin is later converted to melatonin.
      • Melatonin is another hormone implicated in the circadian rhythm. When exposed to darkness, we produce serotonin, which gets converted into melatonin, which signals our bodies that it’s time to sleep. On the other side, when exposed to light in the morning, melatonin production is suppressed and is also produced sooner, helping us to feel more fatigued when it’s time to go to bed.

Why use a SAD lamp

  • Light boxes can be purchased that emit full spectrum light similar in composition to sunlight, usually about 10 000 lux.
    • For comparison, indoor social lighting is rated as less than 100 lux, bright office lighting at 500 lux, outdoors on a cloudy day at 5,000 lux, and outdoors on a sunny day at 50,000 lux or higher.
    • In the winter, the outdoor light intensity can also be much lower depending on where you live. Thus, even if you make the effort of going outside during the winter in the morning hours, you might not get enough sunlight.

How to use a SAD lamp (based on recommendations to treat SAD disorder)

  • When to use it
    • Most studies indicate that early morning treatment (before 8 am) is optimal. As a rule of thumb, use it first thing in the morning.
    • If you cannot use it first thing in the morning, you can use it later, but avoid using it after 12 p.m.
    • Ideally, use it at about the same time every morning, and go to bed and wake up at the same time every day.
    • It is important that light therapy be used consistently on a day-to-day basis including weekends.
    • It can be used from the early fall until spring.
  • Position
    • Sit at about 41 cm of the SAD light.
    • If you’re looking for a medical-grade light therapy lamp, it should point light down from an upward angle. This allows light to reach the top of your eyes, just like the sun does.
    • If it does not point downward, do not look straight into the lamp. Instead, position it at about 45 degrees to the right or left of your eyes.
    • You can read or eat while sitting under the lights, but your eyes must be open for the effect to occur. Indeed, it was shown that melanopsin, a photopigment located in the retina, modulates the circadian effects of light.
  • Duration and lux intensity
    • Beneficial effects have been shown with a 30-minute daily use of 10 000 lux. If you use a lower lux, you will have to use it for longer to reap the same benefits. For example, if you use an intensity of 5 000 lux, you will have to use it for 1 hour. If the intensity if 2 500 lux, it will have to be used for 2 hours.
  • Light spectrum
    • Therapy lamps typically produce blue or full-spectrum light therapy.
    • It has been speculated that short-wavelength (blue-appearing) is more effective than broad-wavelength (white) light. However, a systematic study concluded that subjects treated with blue light for SAD did not improve more than subjects treated with blue-free light.
    • Full-spectrum is similar in composition to sunlight. Blue light has a shorter wavelength and carries more energy, and could cause eye strain.
    • Full-spectrum ranges from 5000K to 6000K. 

Tips when purchasing a SAD light

  • Make sure that the SAD light produces as little UV light as possible.
  • Choose lamps that are anti-glare and anti-flicker, as they can cause eyestrain.
  • SAD lamps are not FDA-regulated. Some SAD lamps claim to provide 10 000 lux, but don’t. You can verify the lux level by downloading an app on your smartphone, like Lux Light Meter Pro: https://play.google.com/store/apps/details?id=com.doggoapps.luxlight&hl=en_CA&gl=US
    • I bought the Verilux® HappyLight® Touch Plus. The app showed 1024 lux. I thought I was not using the application the right way. However, when I hid the light sensor of my phone with my fingers, the lux intensity decreased. I also went outside – and for the record, it was a snowy day, and I live in Canada. It showed 10 015 lux. Needless to say, I had to return my Verilux HappyLight. After doing a quick research, I found 2 brands that seemed to possess most of the characteristics I was looking for: Northern Light Technologies and Carex. I decided to try my luck with Northern Light technologies because they mention on their website that all lamps have a 7-year warranty, have UV protection and Very low EMF, and hold a Medical Device Establishment Licence (MDEL) from Health Canada. Furthermore, they sell panels that can be positioned above the level of the eyes, mimicking the sun. Here is an overview of all their products, which I found very useful (This is not sponsored): https://northernlighttechnologies.ca/product-comparison/

Side effects

  • Light therapy is generally well-tolerated, with headache, nausea, eye strain, and agitation being the most common side effects.
  • Some patients will not be able to tolerate light therapy because of agitation. In these cases, temporarily decreasing the duration of therapy and/or increasing the distance from the light may be considered. As with other effective antidepressants, hypomania can be induced on occasion in individuals with bipolar disorder.
  • There have been case reports of possible ocular damage with bright light treatment, although longer-term follow-up studies have not shown ocular damage with light.
  • Symptoms usually occur at the beginning of treatment and get better in a few days. Otherwise, they can be relieved by reducing the daily exposure time, or by sitting slightly farther away from the lights.

Precautions

  • Patients taking photosensitizing medications or with significant retinal pathology should not be using light therapy. For other ophthalmologic conditions, follow the recommendations of your ophthalmologist.

References

  • Levitan, R. D. (2005). What is the optimal implementation of bright light therapy for seasonal affective disorder (SAD)? Journal of Psychiatry and Neuroscience, 30(1), 72. https://doi.org/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC543845/
  • Campbell, P. D., Miller, A. M., & Woesner, M. E. (2016). Bright Light Therapy: Seasonal Affective Disorder and Beyond. The Einstein journal of biology and medicine : EJBM, 32, E13. https://doi.org/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746555/
  • https://sad.psychiatry.ubc.ca/resources/public-resources/light-therapy-procedure-for-using-the-10000-lux-fluorescent-light-box/
  • Mauri, S., Favaro, M., Bernardo, G., Mazzotta, G. M., & Ziviani, E. (2022). Mitochondrial autophagy in the sleeping brain. Frontiers in Cell and Developmental Biology, 10. https://doi.org/10.3389/fcell.2022.956394
  • Virk, G., Reeves, G., Rosenthal, N. E., Sher, L., & Postolache, T. T. (2009). Short exposure to light treatment improves depression scores in patients with seasonal affective disorder: A brief report. International journal on disability and human development : IJDHD, 8(3), 283. https://doi.org/10.1901/jaba.2009.8-283
  • Melrose, S. (2014). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015. https://doi.org/10.1155/2015/178564
  • Anderson, J., Hilaire, M. S., Auger, R., Glod, C., Crow, S., Rivera, A., Salgado, S. F., Pullen, S., Kaufman, T., Selby, A., & Wolfe, D. (2015). Are Short (Blue) Wavelengths Necessary for Light Treatment of Seasonal Affective Disorder? Chronobiology international , 33 (9), 1267. https://doi.org/10.1080/07420528.2016.1207660