While depressive episodes may occur during the summer months, winter episodes far outnumber summer episodes. Symptoms characteristic of SAD include fatigue, oversleeping, overeating with weight gain and craving for carbohydrates, avoidance of social situations, sensitivity to rejection, heavy feeling in the arms or legs, poor concentration, difficulty completing tasks, and irritability. Many patients begin to notice symptoms as the days shorten, with January and February typically the worse months.
Symptoms begin to improve as days lengthen.
Earlier studies used 2500 lux for 2 - 3 hours. We now know that 10,000 lux for 30 - 90 minutes works just as well. Light therapy works best when used early in the morning, especially when it is still dark outside, but can be used twice daily. Additional light exposure during the afternoon may be helpful for patients who do not respond as well to morning-only use. The light source should be within 4 feet of the eyes.