Bright light therapy has been used for years to treat seasonal affective disorder and depressed patients in general. Patients sit in front of a special lamp which has similar effects on their circadian rhythms or wake cycle as the sun would, thus increasing their energy and lifting their moods. I had great success with my light therapy box during a particularly trying depressive episode several years ago.
Researchers are now speculating that light DEPRIVATION therapy, the opposite of bright light therapy, may be a viable treatment for bipolar mania. Light deprivation therapy can be achieved by limiting exposure to sunlight or by wearing specialized glasses.
There are only a few studies testing this theory, however, and while results of these studies are positive, sample sizes are too small to be generalized. Hopefully, they will continue to look into this further because if it works, it would be a safe, non-invasive option for treating bipolar mania.