Bright light also suppresses the secretion of the night-time hormone melatonin, and may enhance the effectiveness of serotonin and other neurotransmitters. Most people who suffer from SAD or winter blues use a 10,000 lux therapy early in the morning for about one-half hour. 10,000 lux is 20 times the intensity of average indoor lighting. Timing of light therapy varies for each individual. Most people who use a full-size lightbox can reduce their treatment time to an average of 15 minutes per day once they notice a response.
Most people respond within the first week, with complete remission in about two weeks.
The response should be very marked. People awaken earlier and easier, feeling more refreshed and energetic during the day. They sleep better throughout the night, and don't feel exhausted or fatigued. By the second week carbohydrate cravings should disappear. The important factor is the intensity of light that reaches your eyes, not the type of light.