[Bright light therapy].

Bright light is a treatment of choice for seasonal affective disorder. Other indications for bright light therapy have also been tested. These include circadian rhythm sleep disorders, early-morning awakening or sleep-maintenance insomnia in elders and behavioral disturbance or insomnia in organic dementia. In these sleep disorders, the pattern of sleep-wake is misaligned with the patient's circadian system or the external environment, resulting in insomnia. Appropriately-timed exposure to bright light can shift the sleep-wake cycle to earlier or later times, in order to correct for misalignment between the circadian system and the desired sleep-wake schedule. Evidence of the efficacy of bright light was so limited. Further research is needed to determine guidelines for the appropriate timing and safe use of bright light therapy.