SAD, or seasonal affective disorder, is now widely recognised as a medical condition, affecting about 25% of the population. Typical symptoms include: excessive tiredness, weight gain, social withdrawal, depressed mood, irritability, difficulty concentrating, carbohydrate cravings, and decreased libido (sex drive). Research has shown supplementing your exposure to light has benefits not only for Winter Blues, but also Jet Lag, PMS, Bulimia Nervosa, Fatigue, and non-seasonal Major Depression. SAD sufferers find that daily use of a good quality lightbox enough to relieve them of their feelings of lethargy, depression and other related symptoms.