RESPITE FROM SAD: Seasonal affective disorder (SAD) is a type of depression that tends to occur (and recur) as the days grow shorter in the fall and winter. It is believed that affected persons react adversely to the decreasing amounts of light and the colder temperatures as the fall and winter progress. If you feel the effects of SAD, at least 30 minutes of daily exposure to bright light (phototherapy), particularly fluorescent light (yes, florescent), both in the morning and evening, significantly improves depression in people with this seasonal affective disorder.