Everyone gets the blues during the dark days of winter. For those living in colder climates and even those in the Southern hemisphere, it seems as though winter will never end. For some, the feelings of depression that come during the winter seem overwhelming. In these individuals, the depression they experience is valid and can become severe.(1)

Seasonal Affective Disorder (SAD) was first defined in 1984 when NA Rosenthal published a paper in the Archives of General Psychiatry(2) in which he described the disorder and some basic findings of his experience with light therapy. Rosenthal described SAD as being characterized “by recurrent depressions that occur annually at the same time each year.”(2) Since this syndrome was first identified, researchers have published hundreds of studies aimed at unraveling its pathology. Thus far, it has been determined that SAD occurs more often in women with initial episodes in early adulthood.(3)

Theoretical causes of SAD have included elevated melatonin levels,(4) alterations in circadian rhythm,(5) genetic differences in photoreceptors, and glucose metabolism(6). The primary focus of research over the years has been on the body's reaction to light and the lack of light during the winter months. Studies have indicated that there may be a relationship between eye color and light sensitivity whereas those with darker colored eyes tend to consistently react differently than those with light colored eyes.(7) To date, controversies over the role of light continue, as do the controversies over the role of melatonin and serotonin; however light therapy remains consistent as a form of treatment for the disorder.

Because Seasonal Affective Disorder is a seasonal depression, treatment and diagnosis often duplicate those that are provided in a person suffering mild to moderate depression.