Seasonal affective disorder is a form of depression that corresponds with the change of seasons. This condition commonly commences in early fall, becoming worse in winter and alleviating by early spring. A rarer form of SAD begins in late spring and ends at the beginning of fall.
"Winter blues" is a milder version of SAD that is more commonly experienced. SAD is more severe as it's a form of depression and affects daily functioning, mood and self-perception. The symptoms can be overpowering and distressing, interfering with coping ability and everyday life. It's classified as a major depressive disorder with a seasonal pattern.
Those who experience SAD can have depressive symptoms similar to those of major depressive disorders, including feelings of sadness and persistent moodiness, and these symptoms occur daily.
Extreme tiredness, lack of energy and a loss of interest in the activities that previously brought fulfillment are also commonly experienced by those with SAD. Feelings of hopelessness and despair also lead to the affected person becoming less sociable and spending more time alone. People with this disorder sleep much more than average and have increased appetites, with particularly cravings for carbohydrates.1‘Seasonal Affective Disorder.’ https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder/