Some people with depression notice a seasonal pattern to their mood. They become depressed as the sunlight fades in early or late Fall and gradually feel better as Winter turns to Spring. During the depression, they often eat more, especially carbohydrates, and feel tired despite sleeping longer. Sometimes their mood swings in Springtime towards exuberant energy and happiness, or even irritability.
This pattern of depression is called Seasonal Affective Disorder (SAD). Part of the cause is thought to be a problem with the circadian rhythm, which is a clock inside us that sets levels of energy, sleep and appetite. This biological clock is run by hormones and transmitters in our brain, such as melatonin. Our brains use sunlight to set this clock, and likewise people with Seasonal Affective Disorder can use artificial sunlight through a lightbox to correct their circadian rhythm.
Light therapy has been shown to help antidepressants work better, even when used in the summertime and by people with non-seasonal depression . There is also a method called “Wake Therapy” which can improve the benefits of light therapy and make it work faster. Wake Therapy is a specialized method which pairs the lightbox with sleep deprivation on certain nights .
Purchasing a Lightbox
Look for the following features in a lightbox:
Intensity: at least 2,000 lux; 10,000 lux is optimal
Many companies advertise portable boxes, even ones that fit on a visor, but these are usually too small to be useful. This problem abounds when medical products, such as lightboxes, are not regulated by the FDA. Fortunately, a groups of researchers in light therapy have stepped in to guide the public. Their group, the Center for Environmental Therapeutics (CET), has a useful web site at:
The CET has also approved the content at this commercial site, which links to several distributors of light boxes (click on “Where to buy”):
A good choice is the “DayLight XL”, which has the right specifications for a low price ($150-200) and was used in research studies. This product is also available at the cet web site (click “products”) and on Amazon:
Using Your Light Box
Although some products encourage continual use throughout the day, research shows that between 30 minutes and 2 hours of light exposure upon awakening brings the best effect. Bright light in the evening may cancel out the effects of morning light. Try to keep a regular sleep schedule and avoid staying up beyond (click here for advice on keeping better sleep).
Timing is critical in light therapy – in fact if used too late it can disrupt your sleep cycle and cause more depression. Ambient (background) light in the evening has been linked to depression, especially blue-light (to read more about blocking out blue light at night, go to www.lowbluelights.com). There is a self-test which will help you find the optimal time to turn on your light. To take this, go to http://www.cet.org/ and click on “Online Self Assessment” and then AutoMEQ (in case the structure of this site changes, the scale you need is called the “Automated Morningness-Eveningness Questionnaire” or autoMEQ). Don’t stress about the timing too much; keep in mind that earlier is better and the goal is to have bright light in the morning and darkness in the evening.
Bring the directions for your lightbox to your doctor to find out how it should be used for your condition. It is important to sit at the right distance and angle (usually 45 degrees) from the light to get the best dose. It takes about 2 weeks for the full effects of the light to set in, but many people begin to feel better as early as 2-4 days after starting the light.
Side Effects and Precautions
Lightboxes are generally safe. It is important not to stare directly into them as this can strain and even damage your eyes. Let your doctor know if you have any eye diseases. The most common side effect of the lightbox is headache. People with bipolar depression may develop manic symptoms with the lightbox (irritability, extreme happiness, high energy, talkativeness, racing thoughts, insomnia); call your doctor if these occur.
More About Seasonal Affective Disorder
Affective Disorder typically comes on between ages 15 and 30. About 5% of people in the
Light and Bipolar Disorder
Seasonal Affective Disorder is common in people with bipolar disorder; however, if you have bipolar, extra caution must be taken when using bright lights because they can also destabilize mood. Darkness at night is also critical for bipolar, especially “blue light.” Dr. Phelps has written extensively about the effects of light and darkness on bipolar disorder.
 Martiny K, et al. Adjunctive bright light in non-seasonal major depression: results from clinician-rated depression scales. Acta Psychiatr Scand. 2005 Aug;112(2):117-25.
 Golden RN, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry. 2005 Apr;162(4):656-62.
 Martiny K, et al. A 9-week randomized trial comparing a chronotherapeutic intervention (wake and light therapy) to exercise in major depressive disorder patients treated with duloxetine. J Clin Psychiatry. 2012 Sep;73(9):1234-42
—Updated 3/13/13 by Chris Aiken, MD