This article is from the Alternative Medicine Therapies guide.
Bright-light therapy has been used very effectively since the late 1980s to help those suffering from seasonal affective disorder (SAD). Studies show that people with SAD notice significant mood improvement within a week of starting daily morning sessions. Scientists believe that light therapy for SAD works by suppressing daytime elevation of the hormone melatonin (a substance that promotes sleep), and increasing the amount of mood-elevating brain chemical serotonin. Interestingly, these changes in neurotransmitters can reduce carbohydrate cravings and the need for an inordinate amount of sleep--both hallmarks of this form of depression.
Studies also show that bright-light therapy can also be effective for insomnia, helping to restore normal sleep patterns in people who can't fall asleep at night or who wake up too early in the morning (there are dawn/dusk simulators sold by light box companies for this purpose).
Light therapy has also been used to treat the depression associated with PMS, chronic anxiety and panic attacks, severe jet lag, and eating disorders such as anorexia nervosa and bulimia. A specific form of light therapy with ultraviolet radiation is used by dermatologists for psoriasis. This is only done under a physician's direct supervision, however.