Abstract
Multiple studies have shown that the exposure to the light at 2000 lux or more can shift circadian rhythms. Bright light has been found to be effective in treating seasonal affective disorder, delayed sleep phase type disorder, jet lag.
Furthermore, it has been found to improve alertness and cognitive performance in night shift workers. The bright light therapy improves sleep-wake patterns in institutionalized elderly persons.
Evening light exposure improves sleep maintenance in the elderly and reduces sundowning behavior in hospitalized patients with Alzheimer's disease. Affective disorder is characterized by marked decrements in mood often accompanied by disrupted circadian rhythms of sleep, body temperature, hormones, and mood.
The seasonal affective disorder (SAD) is the most overt manifestation of seasonality in humans. It is characterized by recurrent major depressive episodes followed by periods of remission that occur on a seasonal basis.
The gold standard treatment for winter SAD is light therapy. Some studies reported an antidepressant effect of the bright light also in non-seasonal depression (non-SAD)