Seasonal Affective Disorder (SAD), or Winter Depression, is a mood disorder occurring in individuals who are very sensitive to seasonal changes. For these people, the winter blues interferes with their ability to function properly. 

Seasonal Affective Disorder is linked to the activity of the internal body clock. a neural center in the mammalian brain involved in regulating eating, sleeping, socializing and sexual activity. In the winter season, the body clock senses the shortening length of day, and responds by causing mammals to sleep longer and eat more, gaining weight to survive harsh winter conditions. Humans experience these changes as a reduction in energy and a tendency to gain weight in the winter months. 

It is thought that light therapy works by lengthening the perceived day length, restoring the body clock to a summer mode. Properly timed light therapy influences neural pathways in the brain that use serortonin as their primary neurotransmitter. It has has been hypothesized that serotonergic activity in the brain is affected by the influence of light on the activity of the body clock. This is why light therapy is also used sometimes to treat non-seasonal depression, where it has been highly effective. (See Clinical Studies - Depression ) The American Psychiatric Association endorses light therapy as an effective treatment for Seasonal Affective Disorder (SAD), describing it as the treatment of choice for a "seasonal pattern depression." 

While it was originally thought that exposure to bright light is needed to influence brain physiology and reset the body clock, numerous independent studies in laboratories around the world have found that Sunnex Biotechnologies low-intensity light therapy technology influences the body clock as effectively as bright light, but in a safer and more comfortable manner.  .

Lo-LIGHT therapy lamps do not use bright light, but a selected narrow spectrum of  light wavelengths to which the body clock is particularly sensitive. Lo-LIGHT therapy lamps have been used for over 10 years to safely and comfortably help customers feel happier and more energetic through the winter months.   

For additional reference material concerning seasonal depression and Seasonal Affective Disorders click

  Click  for more  information on The Body Clock and Mood