Lack of light causes an increase in the production of Melatonin (the hormone that makes us sleepy at night), and a reduction of Serotonin, the lack of which causes depression. The exposure to bright light therapy reverses the process, with the additional benefit of being drug free. SAD sufferers responded, often quite dramatically, to Bright Light Treatment. Our fully proven lightboxes have been specifically designed and are a recognised method of alleviating S.A.D.