Abstract
The influence of light on the human psyche was known and used two thousand years ago by ancient Greeks. Recently, several scientists started to study light treatment on the basis of chronobiology.
Multiple studies have shown that exposure to light at 2000 lux or more can shift circadian rhythms. Bright light is a treatment of choice for seasonal affective disorder.
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 bright light also in non-seasonal depression (non-SAD).
Other indications for bright light therapy have also been tested. These include bipolar depression, chronic depressive disorder, ante and postpartum depression, late luteal phase dysphoric disorder, circadian phase sleep disorders, jet lag, shift work problems, and behavioral disturbance and insomnia in organic dementia.
Future studies should focus on exploring the use of light therapy in combination with sleep deprivation, other classes of antidepressants, and with psychotherapy and their possible combined effect on subtypes of depression or other mentioned diagnoses, light treatment duration, and the applicability and efficacy of adjunct light treatment for inpatients.