Abstract
The influence of light on human psyche was known and used two thousand years ago by ancient Greeks. The modern development of light treatment and the description of the seasonal affective syndrome were strongly influence by the finding that melatonin in men could be suppressed by bright light.
Shortly after this information was published the first placebo-controlled study on light treatment for depression was done. Now bright light therapy or phototherapy has become the mainstay of the treatment of winter type of seasonal affective disorder.
Seasonal affective disorder (SAD) is typical manifestation of seasonality in humans. It is characterized by recurrent major depressive episodes followed by periods of remission that occur on a seasonal basis.
This pattern of onset and remission must have occurred during the last 2 years, without any nonseasonal episodes occurring during this period. Surveys indicate the prevalence of winter SAD among general population to be between 4 to 9 percent.
As much as 20 percent of the population may have subsyndromal features. Rates of SAD are slightly higher among relatives of those with a confirmed diagnosis of SAD.
SAD patients typically suffer with mild depression. But there are also some cases with severe depression.
Depressive episode that occur in a seasonal pattern are often characterized by prominent anergy and other atypical symptoms like hypersomnia and fatigue, increased appetite and overeating (particularly carbohydrate craving), weight gain, decrease of concentration, irritability and heightened sensitivity to interpersonal rejection. Atypical depressive symptoms, rather than the overall severity of a depressive episode, best predict a good response.
Bright light therapy also has used as an investigational treatment in other psychiatric disorders, but the evidence for its efficacy in these conditions in uncertain. Bright light therapy conventionally means the administration of visible light producing at least 2500 lux at eye level.
It has usually been administered by means of light boxes. Response to daily sessions of phototherapy in SAD generally occurs within 2 to 4 days, and marked improvement is usually achieved within 1 to 2 weeks.