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If you are among the 14 million Americans who experience Seasonal Affective Disorder (SAD), major depression that occurs most often in winter, you may find light therapy an effective treatment.

Humans are hard-wired to be active during daylight and to shut down at night, but our dim workplaces and lamp-lit homes have disturbed our circadian rhythms.

Light therapy may influence the three key neurotransmitters serotonin, dopamine and norepinephrine, says Dr. Norman Rosenthal, who named the disorder.

Here's how light therapy works.

A standard light box is about 24 x 18 inches and contains white fluorescent bulbs behind a diffusing screen to filter out most of the ultraviolet rays. Users sit in front of the box for 20-90 minutes, most of that time as early in the morning as possible. Users should sit so that light falls on open eyes. A therapeutic amount of light is between 2,500 and 10,000 lux. The higher the lux, the shorter the daily treatment required. Begin at the start of winter with 20 minutes of exposure in the morning and add time as days grow longer and symptoms worsen. Users can read, talk on the phone, work out on exercise equipment - as long as the light is falling on open eyes.

Prices for light boxes range from about $170 for the new, smaller blue light boxes to about $200-400 for full-spectrum boxes. Most offer a 30-day return policy, giving you a chance to test their effectiveness.

Light treatment should be done in consultation with a competent and supportive, qualified physician.

Rosenthal says it won't cure all winter ills but more than 80 percent of SAD sufferers can expect some benefit from light therapy and most will begin to feel better after a few days of treatment.

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Side effects of light therapy are not common and are usually easily remedied by reducing treatment time, moving farther from the light box, taking breaks during sessions or changing the time of day you use light therapy. Side effects may include: eyestrain, headaches, sleep disruptions, fatigue, restlessness or irritability. Talk to your doctor for additional help and advice.

Some people experience improvement from increasing their exposure to indoor light from regular lamps and to outdoor light by taking daily walks during the morning or afternoon.

What about blue light? Newer blue light boxes are smaller, cheaper and require less exposure than traditional full-spectrum boxes. But researchers do not agree about the benefits or safety of blue light for light therapy. Some say it is as effective as white light and more comfortable. Preliminary studies suggest that blue light puts out less potentially harmful photons than the older ones, which have a lower peak of emission (small wavelengths, more energy, more potential damage.) Other authorities warn of dangers to the eyes from exposure to blue light.

Current data suggests that the photoreceptors that respond best to light are on the bottom of the retina, so that light coming from above eye level is more effective. Some light boxes have stands that place the light source higher, some are adjustable and the small blue light boxes can be placed on top of something to shine from above.

Sources:
Winter Blues, Revised Edition: Everything You Need to Know to Beat Seasonal Affective Disorder, Norman E. Rosenthal, M.D. The Guilford Press 2002
PsychEducation by Dr. Jim Phelps, author of Why Am I Still Depressed?

Light therapy photos courtesy
Enviro-Med. Enviro-Med designs, manufactures and markets Bio-Lights, used in research centers, hospitals and homes worldwide for the treatment of Seasonal Affective Disorder (SAD)
Apollo Health, manufacturer of blue spectrum light therapy devices.

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