Disclaimer: I feel a bit silly for saying this, but I want to make it clear that I am not now, nor will I ever be, a medical doctor. Therefore, I am not qualified to give professional medical advice. The following is information about how SAD is treated, but it is not meant to be taken as professional medical opinion.
SAD is treated in several ways: light therapy, medication, and environmental change. There’s a lot to say about light therapy so I’m going talk exclusively about light therapy in this post and address medication and environmental change in another post.
Bright Light Therapy
Since SAD is caused by a decrease in sunlight, it seems like a no-brainer to treat people with SAD with light (although insurance companies don’t necessarily agree). A very simple solution is to try to spend more time outdoors. This can certainly help if a person is stricken with SAD because she has started an office job after years of working outside as a park ranger. However, since SAD seems to be triggered by the days getting shorter, simply going outside more (while still a good idea) is not going to be enough to cause remission. So, what’s a SADgirl to do? Use artificial light, of course!
Probably the main form of light therapy is sitting in front of a bright light source (ie a light box). I am not talking about a lamp without a lampshade here. I am talking about a BRIGHT light. According to Winter Blues , regular household bulb emits about 500 lux (lux is a unit of intensity). A therapeutic light source, on the other hand, emits 2,500 to 10,000 lux (just a little bit brighter than a regular bulb!). The amount of light from the sun in a summer sky is 100,000 lux. Fortunately, a person does not need to be exposed to 100,000 lux in order to get relief from SAD!
What color of light should you use? According to the literature, green light is better than red light , white light is somewhat better than green light , and blue light is better than red light . I have not seen a study comparing white light and blue light (or blue light and green light). You can find both white light and blue light boxes on the market and I have heard good things about both. Most of the light boxes I have seen contain full-spectrum bulbs and therefore give off white light. Some of these also give off UV light, so if you get one of these, it is important that it has a UV filter to avoid damage to your eyes and skin.
The amount of time a person needs to sit in front of the light box to get a therapeutic dose varies from person to person and according to what time of year it is. For instance, I use my light box for ten minutes a day in the early fall and max out at an hour a day sometime in February and then taper back down to 10 minutes a day during the spring and nothing at all during the summer. Your mileage may vary. Therefore, a person will need to experiment to see how long they need to sit in front of the light box. In Winter Blues, Dr. Rosenthal suggests starting out at 20 minutes a day for a week and if you do not feel that is benefiting you, move up to about 45 minutes a day .
It is generally recommended that you use the light box in the morning. Using it too late in the day can lead to insomnia (unless you have something called phase-advanced SAD in which using the light box late in the day is more therapeutic than in the morning). You can also split the amount of time you sit in front of the light box to both morning and afternoon. This can help with the afternoon sleepiness that many people with SAD feel (I admit that even people without SAD often feel a little sleepy in the afternoon–and they can probably benefit from a little bright light in the afternoon too!).
One important aspect of bright light therapy is that you must use it every day or every other day. Going two days in a row without light therapy can mean a return of SAD symptoms.
Another type of light therapy can be found in dawn simulators. Dawn simulators do exactly what it sounds like they do—simulate dawn. A dawn simulator is a device that causes a light to turn on and gradually brighten over a period of time. That light may be part of the device, or the device may be a sort of timer that controls a nearby lamp.
Dawn simulators can be invaluable to people with SAD—particularly in helping them wake up in the morning. One study actually concluded that dawn simulation was better than bright light therapy in relieving symptoms of SAD . Personally, while my dawn simulator absolutely necessary for me to wake up in the mornings, the light box is what relieves my depression.
Yes, you read right—vacation. While most people can probably benefit from taking a break from work, the vacation I’m talking about here is a break from the darkness. Going to a sunny location for a week (or more!) in January or February can make a huge difference to SAD sufferers—more so than a vacation spent in a non-sunny locale.
Fortunately, the side effects of bright light therapy are pretty mild which means that the vast majority of SAD sufferers can reap the benefits of light therapy. The side effects include headache, eye strain, irritability, and insomnia. These can mostly be countered by decreasing the amount of time you sit in front of the light box, or using a less powerful light box. Just because the side effects are mild doesn’t mean you shouldn’t discuss light therapy with your doctor, however!
Next: Other forms of treatment.
 Rosenthal, NE. Winter Blues. New York: Guilford Press, 1993; second edition 1998.
 Oren DA, Brainard GC, Johnston SH, Joseph-Vanderpool JR, Sorek E, Rosenthal NE. Treatment of seasonal affective disorder with green light and red light. Am J Psychiatry. 1991 Apr;148(4):509-11.
 Stewart KT, Gaddy JR, Byrne B, Miller S, Brainard GC. Effects of green or white light for treatment of seasonal depression. Psychiatry Res. 1991 Sep;38(3):261-70.
 Glickman G, Byrne B, Pineda C, Hauck WW, Brainard GC. Light therapy for seasonal affective disorder with blue narrow-band light-emitting diodes (LEDs). Biol Psychiatry. 2006 Mar 15;59(6):502-7. Epub 2005 Sep 13.
 Avery DH, Eder DN, Bolte MA, Hellekson CJ, Dunner DL, Vitiello MV, Prinz PN. Dawn simulation and bright light in the treatment of SAD: a controlled study. Biol Psychiatry. 2001 Aug 1;50(3):205-16.