Ever notice a change in your mood when the weather is rainy or overcast? There is a medical term for those feelings. It's called S.A.D is (Seasonal Affective Disorder) and it is a form of depression. Doctors believe the absence of sunlight can cause a deficiency in vitamins and slight, severe, depression. Studies show that if people are exposed to at least 15 minutes of artificial sunlight per day S.A.D symptoms can be avoided.