Light therapy works best when used early in the morning, especially when it is still dark outside, but can be used twice daily. Additional light exposure during the afternoon may be helpful for patients who do not respond as well to morning-only use. The light source should be within 4 feet of the eyes. You should not look directly into the light, but your eyes must be open for light to be effective. There does not appear to be any differences in effectiveness among various wavelengths of light used.
Tanning beds are ineffective and can be dangerous because of the UV light used.
Most people with SAD use light therapy daily during the winter. Most people use lights specifically designed for phototherapy, but some have found 4-lamp fluorescent light fixtures just as effective. The most common side effect is eye irritation, which often responds to increasing the humidity in the house, or sitting farther away from the light. There has been no evidence of long-term damage to the eyes from light therapy. There are other treatments which can be effective for people with SAD who do not or only partially respond to light therapy.