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 the spring towards exuberant energy and happiness, or even irritability.
This pattern is called Seasonal Affective Disorder (SAD). Part of the cause is thought to be a problem with the circadian rhythm, which is the body’s inner clock that sets levels of energy, sleep and appetite. This biological clock is run by hormones and transmitters in our brain, such as melatonin, cortisol, and epinephrine. 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 is one of a few natural treatments that works as powerfully as medication. It even works when used in the summertime or in people who don’t have seasonal depression . It helps ADHD, bulimia, sleep, sex drive, and some medical disorders such as Parkinson’s disease.
Purchasing a Lightbox
Many companies advertise portable boxes, even ones that fit on a visor, but these are usually too small to be useful. This problem is common when medical products, such as lightboxes, are not regulated by the FDA. Fortunately, a group 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: http://www.cet.org/
The CET has also approved the content at this commercial site, which links to several distributors of light boxes: http://www.up-lift.com/newdaylightsite/
Click on “Which Product Should I Use” to compare available devices, and “Where to Buy” to find distributors. The “Insurance Coverage” link can help with reimbursement. Although the Day-Light XL and Day Light Sky, which were made by Up-Lift before 2014 and now by Carex, are low cost models ($130-200), they offer some of the best specifications. The DayLight is also available at Amazon.com (key words to search for in amazon are: “Uplift Daylight”):
The bulbs should be replaced every 2 years (search for Daylight Dl930 Replacement Bulb on Amazon).
If you are using a different brand, look for the following features:
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”):
Using Your Light Box
Timing is critical in light therapy – in fact if used too late in the day it can disrupt your sleep cycle and cause more depression. Evening light has been linked to depression, especially blue-light. There is a self-test that will help you find the optimal time to start light therapy, which ranges from 5:00 a.m. to 8:15 a.m. depending on whether you are a morning person (start it earlier) or a night owl (start it closer to 8 am).
Turning the box on at your optimal time, or within an hour of it, will enhance its antidepressant effects. Don’t give up if you can’t fit it in at that hour though. As long as it’s started in the morning you will still get benefit. Light therapy may have reverse effects - disrupting sleep cycle and causing mood problems - if used too late in the day (e.g. more than 6-8 hours past your ideal time).
If you find it hard to get out of bed and start light therapy in the morning hours, you may be suffering from a symptom of depression called sleep inertia. Pairing the lightbox with a dawn simulator can help you overcome that.
Sit at close range under the box (it should be no more than 14 inches from your head) for 30 minutes. Angle the light so it’s tilted over your head at a 45 degree angle. The goal is to imitate the angle of the sun, and as with the sun you shouldn't look straight into it. Talk with your provider to help individualize your timing - sometimes longer sessions are needed (e.g. 1-2 hours) and sometimes shorter ones are necessary (e.g. lowering to 15 min, stopping altogether, or adding dark therapy if you develop mania, irritability, or agitation with light therapy).
It takes about 2-4 weeks to see the full benefit, but you may see improvement as early as 3 days.
Side Effects and Precautions
Lightboxes are generally safe. Don’t stare directly into them as this can strain and even damage your eyes. Let your provider 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); contact your provider if these occur.
Advanced Light Therapy
Light therapy can be paired with a specialized behavioral technique called Wake Therapy make it work faster and better . Triple-chronotherapy is a recent modification that combines light therapy, wake therapy, and lithium. It can be effective when other treatments for depression have failed to work.
More About Seasonal Affective Disorder
Seasonal Affective Disorder (SAD) typically comes on between ages 15 and 30. About 5% of people in the U.S. have S.A.D., and up to 20% have milder forms of the condition. The rates of SAD are surprisingly as high in North Carolina as they are in the North Eastern states. They start to go down around Columbia, SC and start to disappear down in Florida.
People also have seasonal mood shifts in the few weeks after the daylight savings shift in spring – we lose morning sun when the clock “springs” forward and it takes a little while to readjust. A good book on seasonal moods is Reset Your Inner Clock by Michael Terman, PhD.
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. Some authorities recommend using the box at 12pm for bipolar depression. Darkness at night is also critical for bipolar. 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 11/18/16 by Chris Aiken, MD