Seasonal Affective Disorder (SAD) is a type of winter depression that affects an estimated half a million people every Winter between September and April, in particular during December, January and February. It is caused by a biochemical imbalance in the human being due to the shortening of daylight hours and the lack of sunlight in winter.Susceptible individuals who work in buildings without windows may experience SAD-type symptoms at any time of year. There is a smaller group of individuals who suffer from summer depression. The typical symptoms of SAD include depression, lack of energy, increased need for sleep.

SAD is directly related to the amount of light that is absorbed through the eyesl. Light entering via the eye is thought to modify brain chemistry and physiology. SAD is a real illness that can be effectively treated by art and light therapy or pictures, videos and special video software programs. Light therapy has been shown to be effective in up to 85 per cent of diagnosed cases.