The Light that Lightens Up the Mood

The Light that Lightens Up the Mood

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With spring slowly making its way into our lives, we’re starting to feel more energized with longer sunny days. The truth is that weather can affect our mood, our sleep pattern and our energy levels. It can be normal to feel a certain degree of fatigue from the lengthy cold and gray days of the year; this general feeling is usually manageable. In some cases, this feeling can manifest itself on a whole new level, to the point that it becomes a debilitating condition affecting activities of daily living. We are talking about those of us who are diagnosed with “seasonal affective disorder”, also known as “SAD” or “winter blues”, which is basically a type of depression that reoccurs seasonally during fall and winter months.

If you are affected by SAD, and if you have passed by a light box in the pharmacy aisle, we think that box deserves a second look, as it may just be the right product to lighten up your mood! We’re talking about bright light therapy.

It’s not uncommon for one to look at bright light therapy with skepticism especially when taking into account its price tag. We decided to write an article to lighten up the facts about the use of bright light therapy in adults, so you could plan ahead with your health care professional for the next gloomy season.

What is bright light therapy (BLT)?

It sure isn’t your typical breakfast BLT! Bright light therapy basically consists of limited exposure to artificial bright light that is of similar intensity to that of the outdoors on a sunny day.

It is worthwhile to first discuss the premise of bright light therapy. Imbalances in brain chemicals (neurotransmitters) are a common cause of depressive conditions; nevertheless, there is still much to be learnt about ways that these imbalances occur and the biological processes that are involved. One of the chemicals that contribute to occurrence of SAD is melatonin3,4. Melatonin is involved in setting our biological clock (sleep and wake cycle) or the “circadian rhythm”. Melatonin is a chemical that is naturally released by our body in response to “darkness”; it has sleep-inducing and depressive effects. Light can excite cells in the retina (eye), which essentially send signals to the brain, which in turn prevent release of melatonin. Bright light therapy is thought to essentially inhibit or delay the release of melatonin1,2 . As a result, BLT has the capacity to change the body’s biological clock and it can restore our “circadian rhythm” that appears to be disturbed when one is affected by SAD1,4. In fact, it has been reported that levels of other chemicals that affect our mood (e.g. serotonin, norepinephrine and dopamine) are also affected by the circadian rhythm5. So, the idea is that by adjusting the circadian rhythm, we could restore chemical balance in the brain, which in turn can improve depressive symptoms.

What Does the Evidence Say?

Many studies have looked at whether BLT works or not. Despite their positive results, many of the trials have had limitations in terms of their design, sample sizes and duration of treatment2. In 2005, a meta-analysis (which is a study that analyzes the results of selected randomized clinical trials together) was carried out on efficacy of bright light therapy in mood disorders. This study concluded that BLT was an effective treatment for seasonal affective disorder in adults5. In fact, BLT is recommended as first line treatment for SAD in published clinical guidelines including Canadian clinical guidelines 6,7,8,9.  In addition, the effectiveness of BLT in treating SAD was considered equal to results of trials using drug therapy in treatment of this condition2. In 2006, a Canadian study called Can-SAD directly compared the efficacy of BLT versus an antidepressant drug (fluoxetine) in 96 individuals (age 18-65) affected by SAD over an 8 week period10. This study showed that BLT had similar efficacy to an antidepressant in treatment of SAD, but with the added advantage of fewer side effects. For those of you interested to see how the trial was carried out, check out the trial in our reference section10. The main downside of BLT is its cost when compared to drug therapy11.

How Safe Is BLT?

BLT is generally well tolerated. Reported side effects are limited to headache, eye strain, nausea and agitation1,10. Side effects may be handled by reducing the treatment time or by increasing the distance from the light box. The light box should typically be placed 16 inches (41 cm) away from you and staring directly at the light box should be avoided13.

People who need to strictly avoid BLT without medical advice are those with underlying eye diseases, certain skin conditions, people who are on medications that make the skin sensitive to light.  BLT can put individuals affected by bipolar disorder at risk of experiencing episodes of mania or hypomania13,1.

Tips on Choosing Light Therapy

Here are a few practical tips on choosing a light box:

  1. The light box should be specifically indicated for treatment of SAD.
  2. Make sure the light box emits bright white light as most of the research on SAD has been done using this light. Avoid blue light.
  3. In order to protect your skin, choose a light box that filters out the UV lights.
  4. Keep in mind that effective treatment relies on three components: intensity of light, duration of treatment and timing. Duration of treatment depends on how bright your light box is. The intensity of light is expressed in the unit of lux. Most studies use 10,000 lux, for 30 minutes early in the morning. If you choose to go with a lower intensity box, you will have to increase the treatment time. It may be beneficial to start with shorter treatment time and to gradually increase the time. 

In order for you to have a better idea of what lux represents, consider this: your bedside lamp’s intensity is about 100 lux, home and office lighting is within the range of 200 to 700 lux. On a sunny spring morning, the intensity of light can range from 2,000 to 10,000 lux and in the summer, we may be exposed to intensities as high as 100,000 lux12. Therefore, the required daily treatment time depends on the intensity of your light box.

BLT for Other Conditions

You may hear about the use of BLT for other conditions such as sleep disorders, non-seasonal depression, alzheimer’s disease or jet lag amongst others. The evidence on use of BLT for conditions other than SAD is not yet clear. One exception is non-seasonal depression. There is actually good evidence on the use of BLT in non-seasonal depression2,4, but current studies only support its use in combination with antidepressants and not yet as stand-alone treatment4.

Researchers are looking at the possibility of using BLT in improving sleep, mood and motor function in elderly patients with Parkinson’s disease1. There are also preliminary studies looking at BLT as an add-on treatment in patients with certain types of epilepsy for reducing seizure frequencies14. However, we still have to wait a while before research brings into light new evidence. 

Bottom Line

BLT is a safe treatment option that is just as effective as drug therapy in treatment of SAD. It may also be used in combination with medications or alternative therapies in treatment of other conditions. Given its safety, it definitely merits a discussion with your health care professional to see if it can be right for you!

The Health Aisle Team


  1. Rutten S, Vriend C, et al. (2012). Bright light therapy in Parkinson’s disease. An overview of the background and evidence. Parkinson’s disease, 2012; ID: 767105, 9 pages.
  2. Golden RN, Gaynes BN, Ekstrom RD, et al. (2005). The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. American Journal of Psychiatry, 162(4): 656–662.
  3. Lam RW, Levitan RD (2000). Pathophysiology of seasonal affective disorder: a review. J Psychiatry Neurosci, 25: 469-480.
  4. Even C, Schroder, CM, Friedman S, Rouillon F (2008). Efficacy of light therapy in nonseasonal depression: A systematic review. Journal of Affective Disorders, 108: 11-23.
  5. McClung CA (2007). Circadian genes, rhythms, and biology of mood disorders. Pharmacology and Therapeutics, 114(2):222-232.
  6. Lam RW, Levitt AJ (1999). Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder. Vancouver, Clinical and Academic Press Publishing.
  7. Ravindran AV, Lam RW, Filteau MJ, et al. (2009) Canadian Network for Mood and Anxiety Treatments (CANMAT) Clinical guidelines for the management of major depressive disorder in adults. V. Complementary and alternative medicine treatments. Journal of Affective Disorders, 117(1): S54–S64.
  8. Bauer M, Whybrow PC, Angst J, Versiani M, Moller H-J. (2002). World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for biological treatment of unipolar depressive disorders, part 1: acute and continuation of treatment of major depressive disorder. World J Biol Psychiatry, 3: 5-43.
  9. American Psychiatry Association: Practice guideline for the treatment of patient with major depressive disorder (2000). Am J Psychiatry, 157:1-45.
  10. Lam RW, Levitt AJ, Levitan RD, Enns MW, et al (2006). The Can-SAD study: A randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with seasonal affective disorder. Am J Psychiatry, 163: 805-812.
  11. Cheung A, Dewa C, Michalak EE, et al. (2012). Direct health care costs of treating seasonal affective disorder: A Comparison of light therapy and Fluoxetine. Depression Research and Treatment, 2012: 5 pages.
  12. The NorthernLight Technologies.
  13. Levitan R (2005). What is the optimal implementation of bright light therapy for seasonal affective disorder (SAD)? Rev Psychiatr Neurosci, 30 (1).
  14. Baxendale SA (2011). Light therapy as a treatment for epilepsy. Med. Hypotheses, 76(5): 661-4.