Does a white Christmas leave you feeling blue? Do you have no energy or motivation? These are all signs of the wintertime blues - otherwise known as Seasonal Affective Disorder (SAD) - that get even the best of us during the long, winter months when the days are short and temperatures are frigid.
According to Dr. Norman Rosenthal, psychiatrist and author of the "Winter Blues," up to 18 million Americans suffer from the condition each year.
SAD can be attributed to a few causes for those who are vulnerable: genetic susceptibility, environmental factors and the lack of light.